Researcher Database

Tanioka Yuichiro
Faculty of Science Institute of Seismology and Volcanology
Professor

Researcher Profile and Settings

Affiliation

  • Faculty of Science Institute of Seismology and Volcanology

Job Title

  • Professor

URL

J-Global ID

Research Interests

  • 津波数値計算   1894年根室半島沖地震   千島の津波波形記録   NOAAの津波波形記録   2006年中千島地震津波   北海道一千島沈み込み帯   1918年千島地震津波   1918年中千島地震   2007年千島沖地震   1973年根室沖地震   2004年釧路沖地震   1894年根室沖地震   2006年千島沖地震   カムチャッカの津波   津波   トモグラヒイ   広帯域地震観測   トモグラフィ   ロシア極東   室戸岬沖   水圧計   宮城県沖地震   海底水圧計   余効変動   上部マントル構造   アスペリティ   釧路   十勝   地殻変動   震源過程   

Research Areas

  • Natural sciences / Solid earth science

Academic & Professional Experience

  • 2009/04 - Today 北海道大学 大学院・理学研究院 教授

Research Activities

Published Papers

  • Yuichiro Tanioka, Naoki Uchida, Aditya Riadi Gusman, Masanobu Shishikura, Takuya Nishimura
    Earth, Planets and Space 73 (1) 1343-8832 2021/12
  • Yusuke Yamanaka, Yuichiro Tanioka
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 126 (5) 2169-9313 2021/05 
    A tsunami that followed the 1906 Colombia-Ecuador megathrust earthquake was observed and recorded by several tide gauges. In this study, tide gauge records were first digitized from documents comparing the estimated astronomical tide level changes, and the observed tsunami waveforms were extracted. An inverse analysis was conducted using the observed tsunami waveforms, and we successfully developed a slip distribution model that produced improved tsunami waveforms for tide gauge stations compared with previous studies. Based on a comparison of the developed source model and ruptured areas of other significant earthquakes around Colombia and Ecuador, the 1906 earthquake already ruptured an area affected by the 1979 earthquake, resulting in a substantial release of accumulated slip deficits. In contrast, although the ruptured area of the 1906 earthquake likely covered the source areas of the 1958 and 1942 earthquakes, the release in these areas during the earthquake was moderate and insignificant, and large slip deficits remained after the 1906 earthquake. These results demonstrate that the extent of the release of accumulated slip deficits varied greatly in the source area of the 1906 earthquake.
  • Yuichiro Tanioka
    Earth, Planets and Space 72 (1) 1343-8832 2020/12/01 [Refereed][Not invited]
     
    © 2020, The Author(s). Since the installation of a dense cabled observation network around the Japan Trench (S-net) by the Japanese government that includes 150 sensors, several tsunami forecasting methods that use the data collected from the ocean floor sensors were developed. One of such methods is the tsunami forecasting method which assimilates the data without any information of earthquakes. The tsunami forecasting method based on the assimilation of the ocean-bottom pressure data near the source area was developed by Tanioka in 2018. However, the method is too simple to be used for an actual station distribution of S-net. To overcome its limitation, we developed an interpolation method to generate the appropriate data at the equally spaced positions for the assimilation from the data observed at sensors in S-net. The method was numerically tested for two large underthrust fault models, a giant earthquake (Mw8.8) and the Nemuro-oki earthquake (Mw8.0) models. Those fault models off Hokkaido in Japan are expected to be ruptured in the future. The weighted interpolation method, in which weights of data are inversely proportional to the square of the distance, showed good results for the tsunami forecast method with the data assimilation. Furthermore, results indicated that the method is applicable to the actual observed data at the S-net stations. The only limitation of the weighted interpolation method is that the computed tsunami wavelengths tend to be longer than the actual tsunamis wavelength.[Figure not available: see fulltext.]
  • Satoshi Kusumoto, Kentaro Imai, Ryoko Obayashi, Takane Hori, Narumi Takahashi, Tung Cheng Ho, Karen Uno, Yuichiro Tanioka, Kenji Satake
    Seismological Research Letters 91 (5) 2624 - 2630 0895-0695 2020/09 
    We estimated the origin time of the 1854 Ansei-Tokai tsunami from the tsunami waveforms recorded at three tide gauge stations (Astoria, San Francisco, and San Diego) on the west coast of North America. The tsunami signal is apparent in the San Francisco and San Diego records, and the arrival time was 0-1 p.m. Greenwich Mean Time (GMT) on 23 December 1854, whereas the tsunami signal of Astoria is ambiguous, and the arrival time could not be determined from the waveform. The simulated waveforms on the basis of nonlinear dispersive wave theory by assuming an origin time of 0 a.m. GMT on 23 December arrived earlier than the observations. Cross-correlation functions between the observed and simulated waveforms recorded at San Francisco and San Diego showed a time gap between them of approximately 30 min. Based on these results, we concluded that the origin time of the 1854 Ansei-Tokai tsunami was approximately 00:30 a.m. GMT or 09:46 local time on 23 December. Our result is roughly consistent with reports by a Russian frigate anchored in Shimoda Bay, ranging the earthquake between 09:00 and 09:45 and the tsunami between 09:30 and 10:00. The earthquake was also reported in historical Japanese documents ranging from 8 and 10 o'clock in local time.
  • Ayumu Mizutani, Kiyoshi Yomogida, Yuichiro Tanioka
    Journal of Geophysical Research: Oceans 125 (9) 2169-9275 2020/09/01 [Refereed][Not invited]
     
    ©2020. American Geophysical Union. All Rights Reserved. Offshore real-time ocean bottom networks of seismometers and ocean bottom pressure (OBP) gauges have been recently established such as DONET and S-net around the Japanese islands. One of their purposes is to practice rapid and accurate tsunami forecasting. Near-fault OBP records, however, are always contaminated by nontsunami components such as sea-bottom acceleration change until an earthquake stops its fault or sea-floor motions. This study proposes a new method to separate tsunami and ocean bottom displacement components from coseismic OBP records in a real-time basis. Associated with the Off-Mie earthquake of 2016 April 1, we first compared OBP data with acceleration, velocity, and displacement seismograms recorded by seismometers at common ocean bottom sites in both time and frequency domains. Based on this comparison, we adopted a band-pass filter of 0.05–0.15 Hz to remove ocean-bottom acceleration components from the OBP data. Resulting OBP waveforms agree well with the tsunami components estimated by a 100-s low-pass filter with records of several hundred seconds in length. Our method requires only an early portion of a given OBP record after 30 s of an origin time in order to estimate its tsunami component accurately. Our method enhances early tsunami detections with near-fault OBP data; that is, it will make a tsunami forecasting system faster and more reliable than the previous detection schemes that require data away from source regions or after coseismic motions are over.
  • Yuichiro Tanioka, Ulbert Gleb Grillo, Greyving Jose Arguello
    Coastal Engineering Journal 62 (3) 350 - 361 2166-4250 2020/07/02 [Refereed][Not invited]
     
    © 2019 Japan Society of Civil Engineers. A near-field tsunami inundation forecast method (NearTIF) for the Pacific coast of Central America is developed and tested on the basis of the 1992 Nicaragua tsunami earthquake case. The appropriate source model of the 1992 Nicaragua earthquake, estimated using the W-phase inversion with a depth dependent rigidity curve from a previous study, is used as a reference model to test the proposed NearTIF method. The tsunami inundation along the Pacific coast of Nicaragua is computed from the reference model of the 1992 Nicaragua earthquake. The tsunami inundation obtained using the NearTIF method matches the tsunami inundations computed from the reference model. The tsunami heights and the tsunami inundation of the 1992 Nicaragua tsunami surveyed by a previous study are roughly matched by the tsunami inundations obtained using the NearTIF method in this study. Although the computational time for the tsunami inundation from the reference source model is about 95 min, the computational time plus the database search time for the NearTIF method is approximately 2–4 min. The method presented in this study can be used as a near-real time tsunami inundation forecast method for the Pacific coast of Central America.
  • Yuichiro Tanioka, Amilcar Geovanny Cabrera, Greyving Jose Arguello, Yusuke Yamanaka
    Coastal Engineering Journal 62 (3) 405 - 412 2166-4250 2020/07/02 [Refereed][Not invited]
     
    © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. In 2018, a large earthquake (Mw7.6) occurred in the Swan Island Fault zone at the northwest boundary of the Caribbean plate. This earthquake generated a small tsunami of 20 cm. However, Puerto Cortes in Honduras is located close to the Swan Island Fault zone. Evaluation of tsunami hazard at Puerto Cortes due to large earthquakes along the fault zone is important. We first estimated the fault parameters of the 2018 Swan Island earthquake using W-phase inversion technique. Then, the moment magnitude of 7.6, the fault length of 134 km, the fault width of 24 km, and the slip amount of 5.1 m were estimated. In addition to those estimates, a small fault dimension of the earthquake, 40 km × 20 km, with a slip amount of 20.8 m was considered. Those two fault models were used to compute tsunami inundation at Puerto Cortes. The tsunami computed from the small fault inundated a large area in Puerto Cortes including the port area. The effect of co-seismic horizontal displacement of ocean floor also enhanced the tsunami inundation at Puerto Cortes. Those results indicate that preparation for future tsunami hazard in Puerto Cortes is important although no significant tsunami was generated historically.
  • Rinda Nita Ratnasari, Yuichiro Tanioka, Aditya Riadi Gusman
    Pure and Applied Geophysics 177 (6) 2551 - 2562 0033-4553 2020/06/01 [Refereed][Not invited]
     
    © 2020, The Author(s). In the subduction zone off the west coast of central Sumatra, two great earthquakes, the 2007 great Bengkulu earthquake (Mw 8.4) and the 2010 Mentawai tsunami earthquake (Mw 7.8), occurred along the plate interface. Although the moment magnitude of the 2010 earthquake was much smaller than that of the 2007 earthquake, the tsunami heights resulting from the former 2010 earthquake were higher than those resulting from the latter 2007 earthquake, indicating that tsunami heights are difficult to forecast. An advanced method for determining appropriate source models that can explain the tsunami heights along coastal areas is needed for tsunami warning purposes. In this study, fault parameters were estimated from the W-phase inversion, and fault length and width were calculated from suitable scaling relations between those and the magnitude for the 2007 and 2010 earthquakes. Tsunami numerical simulations were conducted using various slip amounts or corresponding rigidities. The best slip amount or corresponding rigidity was selected by comparing the measured and computed tsunami heights. For the 2007 Bengkulu earthquake, the measured tsunami heights are well explained using a rigidity of 3.0 × 1010 Nm−2 (7.59-m slip amount). For the 2010 Mentawai tsunami earthquake, the measured tsunami heights are well explained using a rigidity of 1.5 × 1010 Nm−2 (8.17-m slip amount). From those results, we determined the depth-dependent rigidity relation for Central Sumatra to estimate appropriate source models in our tsunami height forecasting method.
  • Utku Kânoğlu, Yuichiro Tanioka, Emile A. Okal, Maria Ana Baptista, Alexander B. Rabinovich
    Pure and Applied Geophysics 177 (3) 1183 - 1191 0033-4553 2020/03/01 [Refereed][Not invited]
     
    © 2020, Springer Nature Switzerland AG. Following the first volume (PAGEOPH, 2019, 176, No. 7), twenty-four papers on tsunamis are included in the PAGEOPH topical issue “Twenty five years of modern tsunami science following the 1992 Nicaragua and Flores Island tsunamis: Volume II,” reporting on the frontiers of tsunami science and research. The first two papers overview meteorological tsunamis, discussing progress since the 1992 Daytona event, and examining the March 2017 Persian Gulf destructive event. The next four papers review historical tsunami events, starting with a paper providing statistics for the last 120 years. The 2018 Kodiak event is investigated in the following two papers. A set of five papers discusses tsunami-warning methodologies specifically for the Australia and Nankai (Japan) regions, and general tsunami warning approaches. Probabilistic tsunami hazard assessment including case studies for two Australian coasts and the Pacific Coast of Central America, as well as discussion regarding the effect of shallow slip amplification uncertainty, and tsunami hazard assessment for the Port of Ensenada, Baja California, are presented in the next five papers. Two papers discuss tsunami tide interaction, and the following two investigate landslide-generated tsunamis, specifically a tsunami landslide scenario study for the Maltese Islands, and the 1694 Ambon, Indonesia tsunami. Tsunami hydrodynamics studies investigating shoaling on steep continental slopes and transmission of long surface, and tsunami-like waves are presented in the last two papers.
  • SHITO Azusa, NAKAMOTO Manami, MIYAMACHI Rintaro, ICHIYANAGI Masayoshi, OHZONO Mako, OKADA Kazumi, KATSUMATA Kei, TAKADA Masamitsu, TAKAHASHI Hiroaki, TANIOKA Yuichiro, YAMAGUCHI Teruhiro, MITSUOKA Ayaho, KOSUGA Masahiro, AZUMA Ryosuke, UCHIDA Naoki, EMOTO Kentaro, OHTA Yusaku, OKADA Tomomi, KAIDA Toshiki, KOZONO Tomofumi, SUZUKI Syuichi, TAKAGI Ryota, MATSUMOTO Satoshi, DEMACHI Tomotsugu, NAKAHARA Hisashi, NAKAYAMA Takashi, HIRAHARA Satoshi, MATSUZAWA Toru, MIURA Satoshi, YAMAMOTO Mare, IMANISHI Kazutoshi, UCHIDE Takahiko, YOSHIMI Masayuki, MATSUSHIMA Takeshi, AOI Shin, ASANO Youichi, UENO Tomotake, FUJITA Eisuke, ABE Eiji, IIDAKA Takashi, IWASAKI Takaya, KATO Aitaro, KURASHIMO Eiji, SAKAI Shin'ichi, AIZAWA Koki, SHIINA Takahiro, SERIZAWA Masato, TANAKA Shinichi, NAKAGAWA Shigeki, HIRATA Naoshi, MASUDA Masataka, MIYAKAWA Koji, YAGI Takeo, WATANABE Atsushi, GOTO Kazuhiko, SHIMIZU Hiroshi, ITO Takeo, OKUDA Takashi, TERAKAWA Toshiko, HORIKAWA Shinichiro, MAEDA Yuta, MATSUHIRO Kenjiro, YAMANAKA Yoshiko, WATANABE Toshiki, IIO Yoshihisa, KATAO Hiroshi, UCHIDA Kazunari, KANO Yasuyuki, TSUDA Hiroo, MIURA Tsutomu, MURAMOTO Tomoya, YAMASHITA Yusuke, OKUBO Makoto, YAMASHINA Tadashi, OHKURA Takahiro, NAKAO Shigeru, HIRANO Shuichiro, KAMIZONO Megumi, MIYAMACHI Hiroki, YAKIWARA Hiroshi, TEGURI Yoshiko
    Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 公益社団法人 日本地震学会 73 149 - 157 0037-1114 2020
  • Yuichiro Tanioka, Shingo Yoshida, Takao Ohminato, Aitaro Kato, Noriko Kamaya
    Journal of Disaster Research 15 (2) 69 - 69 1881-2473 2020 [Refereed][Not invited]
  • Reo Kimura, Hiroe Miyake, Keiko Tamura, Naoyuki Kato, Yuichi Morita, Masato Iguchi, Yuichiro Tanioka, Kazuki Koketsu, Yoshihiko Kuroda, Hiromitsu Oshima, Kenji Satake
    Journal of Disaster Research 15 (2) 152 - 164 1881-2473 2020 [Not refereed][Not invited]
     
    © 2020, Fuji Technology Press. All rights reserved. In order to contribute to the field of disaster science, various research in Japan currently focus on the clarification of the phenomenon called “disaster.” Due to society’s demand for disaster prevention and disaster mitigation, these researches are carried out through collaboration among researchers in science, engineering, humanities, social sciences, etc. These research outcomes are aimed at the following: verification of disaster cases of earthquakes and volcanic eruptions; clarification of the disaster occurrence mechanisms of earthquakes and volcanic eruptions; sophistication of information for disaster mitigation of earthquakes and volcanic eruptions; and development of researchers, engineers, and human resources involved in disaster prevention operations and disaster prevention responses. This article puts these research outcomes to-gether from four points of view: 1) research on earthquakes and volcanic eruptions disaster cases, 2) clarification of disaster occurrence mechanisms of earthquakes and volcanic eruptions, 3) sophistication of information for disaster mitigation of earthquakes and volcanic eruptions, and 4) development of researchers, engineers, and human resources involved in disaster prevention operations and disaster prevention responses.
  • Yuichiro Tanioka, Mizuho Shibata, Yusuke Yamanaka, Aditya Riadi Gusman, Kei Ioki
    Progress in Earth and Planetary Science 6 (1) 2197-4284 2019/12/01 [Refereed][Not invited]
     
    © 2019, The Author(s). The 2011 Tohoku-oki earthquake generated a large tsunami that caused catastrophic damage along the Pacific coast of Japan. The major portion of the damage along the Pacific coast of Tohoku in Japan was mainly caused by the first few cycles of tsunami waves. However, the largest phase of the tsunami arriving surprisingly late in Hakodate in Hokkaido, Japan; that is, approximately 9 h after the origin time of the earthquake. It is important to understand the generation mechanism of this large later phase. The tsunami was numerically computed by solving both linear shallow water equations and non-linear shallow water equations with moving boundary conditions throughout the computational area. The later tsunami phases observed on southern Hokkaido can be much better explained by tsunami waveforms computed by solving the non-linear equations than by those computed by solving the linear equations. This suggests that the later tsunami waves arrived at the Hokkaido coast after propagating along the Pacific coast of the Tohoku region with repeated inundations far inland or reflecting from the coast of Tohoku after the inundation. The spectral analysis of the observed waveform at Hakodate tide gauge shows that the later tsunami that arrived between 7.5 and 9.5 h after the earthquake mainly contains a period of 45–50 min. The normal modes of Hakodate Bay were also computed to obtain the eigen periods, eigenfunctions, and spatial distribution of water heights. The computed tsunami height distributions near Hakodate and the fundamental mode of Hakodate Bay indicate that the large later phases are mainly caused by the resonance of the bay, which has a period of approximately 50 min. The results also indicate that the tsunami wave heights near the Hakodate port area, the most populated area in Hakodate, are the largest in the bay because of the resonance of the fundamental mode of the bay. The results of this study suggest that large future tsunamis might excite the fundamental mode of Hakodate Bay and cause large later phases near the Hakodate port. [Figure not available: see fulltext.].
  • Kei Ioki, Yuichiro Tanioka, Gentaro Kawakami, Yoshihiro Kase, Kenji Nishina, Wataru Hirose, Kei’ichi Hayashi, Ryo Takahashi
    Earth, Planets and Space 71 (1) 1343-8832 2019/12/01 [Refereed][Not invited]
     
    © 2019, The Author(s). Tsunami deposits were collected along the coast of southwestern Hokkaido and Okushiri Island, northern Japan. The distribution of these deposits suggested that large earthquakes and tsunamis have repeatedly occurred off southwestern Hokkaido. Along the southern coast of Okushiri Island, five tsunami sand/gravel layers have been deposited during the last 3000 years. The latest was deposited by the 1741 Oshima–Oshima landslide tsunami and the second by the 12th century tsunami. The later tsunami was probably generated by a large earthquake because submarine seismo-turbidites with similar age exist in the region and a large inland landslide had occurred in Okushiri Island in approximately the 12th century. The ages of paleo-tsunami events prior to the 12th century are 1.5–1.6, 2.4–2.6, 2.8–3.1 ka. In this study, a fault model of the 12th century earthquake was estimated by comparing tsunami deposit distributions and calculated tsunami inundation areas at five sites in Okushiri Island and Hiyama region. Fault model F17, a submarine active fault in the Japan Sea near Oshima–Oshima, is a probable source for this tsunami. Numerical simulation of the tsunami was performed based on fault model F17; we modified the fault parameters (length and slip amount) from the original model to explain tsunami deposit distributions. A shorter length of 104 km and a larger slip amount of 18 m were appropriate for the fault model on the basis of parametric studies. The seismic moment of the earthquake was calculated to be 9.95 × 1020 Nm (Mw 7.9) assuming a rigidity of 3.43 × 1010 N/m2. The estimated fault model is located between the focal regions of the 1993 Hokkaido Nansei-oki earthquake and the 1983 Japan Sea earthquake.
  • Nobutomo Osanai, Takashi Yamada, Shin ichiro Hayashi, Shin’ya Kastura, Takahisa Furuichi, Seiji Yanai, Yasuhiro Murakami, Tomoyoshi Miyazaki, Yuichiro Tanioka, Shigetaka Takiguchi, Mayumi Miyazaki
    Landslides 16 (8) 1517 - 1528 1612-510X 2019/08/01 [Refereed][Not invited]
     
    © 2019, Springer-Verlag GmbH Germany, part of Springer Nature. The 2018 Hokkaido Eastern Iburi Earthquake struck the eastern Iburi region (epicenter: 42.691°N, 142.007°E, depth: 37.0 km) of Hokkaido, Japan, at 3:07.59 JST, September 6, 2018 (18:07.59, September 5, 2018 UTC). Many shallow landslides were triggered by this Mw 6.6 (Mj 6.7) earthquake. The basement complex in the affected area (sedimentary rocks) is covered with thick pyroclastic fall deposits derived from the Tarumae Volcano, etc., and the strong seismic shocks triggered shallow landsliding of them. Shallow landslides moving along valley type topography traveled greater distances than those moving along planar slope topography. Some shallow landslides occurred on relatively gentle slopes (< 30°). The earthquake also induced several large-scale deep-seated landslides, including one that has formed a landslide dam in the Hidaka-horonai River. Landslides were densely distributed over hilly regions (elevation: 200–400 m) within an area of approximately 400 km2 in Atsuma (landslides caused 36 deaths), Abira, and Mukawa, and the number of landslides and the total area of the landslides were the largest in Japan ever since the Meiji Era (1868–1912). The catchments where shallow landslides were concentrated were severely devastated.
  • Utku Kânoğlu, Yuichiro Tanioka, Emile A. Okal, Maria Ana Baptista, Alexander B. Rabinovich
    Pure and Applied Geophysics 176 (7) 2757 - 2769 0033-4553 2019/07/01 [Refereed][Not invited]
     
    © 2019, Springer Nature Switzerland AG. Twenty-two papers on tsunamis are included in the Pure and Applied Geophysics topical issue “Twenty five years of modern tsunami science following the 1992 Nicaragua and Flores Island tsunamis: Volume I,” reporting on the frontiers of tsunami science and research. The first three papers overview significant tsunamis of 1992–2018 and discuss the problems of tsunami cataloguing. The main focus of the next four papers is on specific details of historical tsunami events and field surveys. First, three papers are related to thorough analyses of several historical events based on macroseismic, seismological, and tsunami observations, tide gauge data, and modelling results: the 1907 Sumatra “tsunami earthquake,” the 1941 Andaman Islands earthquake, and five great tsunamis in the Pacific Ocean (1946, 1952, 1957, 1960 and 1964). The last paper of the section concerns results of the field survey of the 2017 Bodrum-Kos tsunami. The reconstruction of the tsunami sources is the main target of the four following papers, with four events examined in detail: the historical 1810 Baja California, 1992 Flores Island, 2012 Haida Gwaii and 2015 Chilean (Illapel) tsunamis. A set of three papers address problems associated with landslide-generated tsunamis in three different regions: a modelling of the 2017 landslide and tsunami at Karrat Fjord, Greenland; a probabilistic analysis of the hazard from the Indus Canyon in the NW Indian Ocean; and a study of the landslide-induced tsunami hazard along the US East Coast. The next section, including three papers, reports on comparisons between different types of tsunami models, on numerical modelling of tsunami waves in the Caspian Sea, and on the modelling of magnetic signals at Easter Island, following the 2010 and 2015 Chilean tsunamis. The last group of five papers discusses tsunami hazard assessment and warning for various regions of the world oceans, including Alaska, the eastern and western Mediterranean, Australia, the Northeast Atlantic and the entire Pacific Ocean; one specific aspect of these studies is the compilation and efficient application of observed data, in particular, from DARTs.
  • Kei Ioki, Yuichiro Tanioka, Gentaro Kawakami, Yoshihiro Kase, Kenji Nishina, Wataru Hirose, Kei'ichi Hayashi, Ryo Takahashi
    EARTH PLANETS AND SPACE 71 1880-5981 2019/05 [Refereed][Not invited]
     
    Tsunami deposits were collected along the coast of southwestern Hokkaido and Okushiri Island, northern Japan. The distribution of these deposits suggested that large earthquakes and tsunamis have repeatedly occurred off southwestern Hokkaido. Along the southern coast of Okushiri Island, five tsunami sand/gravel layers have been deposited during the last 3000years. The latest was deposited by the 1741 Oshima-Oshima landslide tsunami and the second by the 12th century tsunami. The later tsunami was probably generated by a large earthquake because submarine seismo-turbidites with similar age exist in the region and a large inland landslide had occurred in Okushiri Island in approximately the 12th century. The ages of paleo-tsunami events prior to the 12th century are 1.5-1.6, 2.4-2.6, 2.8-3.1ka. In this study, a fault model of the 12th century earthquake was estimated by comparing tsunami deposit distributions and calculated tsunami inundation areas at five sites in Okushiri Island and Hiyama region. Fault model F17, a submarine active fault in the Japan Sea near Oshima-Oshima, is a probable source for this tsunami. Numerical simulation of the tsunami was performed based on fault model F17; we modified the fault parameters (length and slip amount) from the original model to explain tsunami deposit distributions. A shorter length of 104km and a larger slip amount of 18m were appropriate for the fault model on the basis of parametric studies. The seismic moment of the earthquake was calculated to be 9.95x10(20) Nm (M-w 7.9) assuming a rigidity of 3.43x10(10)N/m(2). The estimated fault model is located between the focal regions of the 1993 Hokkaido Nansei-oki earthquake and the 1983 Japan Sea earthquake.
  • Kei Ioki, Yuichiro Tanioka, Hideaki Yanagisawa, Gentaro Kawakami
    Journal of Geophysical Research: Solid Earth 124 (2) 1991 - 2002 2169-9313 2019/02 [Refereed][Not invited]
     
    ©2019. American Geophysical Union. All Rights Reserved. Sector collapse during the 1741 eruption of Oshima-Oshima volcano (southwestern Hokkaido, Japan) generated a large tsunami in the Japan Sea. The tsunami caused severe damage along the Oshima (Hokkaido) and Tsugaru (Honshu) peninsulas. Tsunami deposits due to the 1741 event were identified along the Okushiri and Hiyama coast in Hokkaido. In this study, we numerically simulated the landslide and tsunami generated by the 1741 Oshima-Oshima eruption using an improved two-layer model to explain the depositional area of the landslide, the tsunami heights written in historical records, and the distributions of tsunami deposits. Areas of erosion and deposition by the 1741 landslide were estimated from the bathymetric data on the northern slope of Oshima-Oshima volcano. In addition, previous topography before the sector collapse was restored. From the bathymetry difference before and after the landslide, the volume of collapsed material was estimated at 2.2 km 3 . Based on those data, the landslide and tsunami were numerically simulated by solving equations of an improved two-layer model that incorporates Manning's formula in the bottom friction terms of the lower layer. An apparent friction angle of 2.5 and a Manning's roughness coefficient of 0.15 were selected to explain the area of deposition estimated from the bathymetry analysis and distributions of tsunami deposits. The thickness distribution of the computed landslide mass fits relatively well with the depositional area. Computed tsunami heights match those from historical records along the Hiyama coast. Computed tsunami inundation areas cover most of the distributions of tsunami deposits identified along the coasts.
  • Mayu Inoue, Yuichiro Tanioka, Yusuke Yamanaka
    Geosciences (Switzerland) 9 (7) 2076-3263 2019 [Refereed][Not invited]
     
    © 2019 by the authors. Licensee MDPI, Basel, Switzerland. A dense cabled observation network, called the seafloor observation network for earthquakes and tsunami along the Japan Trench (S-net), was installed in Japan. This study aimed to develop a near-real time tsunami source estimation technique using the ocean bottom pressure data observed at those sensors in S-net. Synthetic pressure waveforms at those sensors were computed for 64 earthquake tsunami scenarios with magnitude ranging between M8.0 and M8.8. The pressure waveforms within a time window of 500 s after an earthquake were classified into three types. Type 1 has the following pressure waveform characteristic: the pressure decreases and remains low; sensors exhibiting waveforms associated with Type 1 are located inside a co-seismic uplift area. The pressure waveform characteristic of Type 2 is that one up-pulse of a wave is within the time window; sensors exhibiting waveforms associated with Type 2 are located at the edge of the co-seismic uplift area. The other pressure waveforms are classified as Type 3. Subsequently, we developed a method to estimate the uplift area using those three classifications of pressure waveforms at sensors in S-net and a method to estimate earthquake magnitude from the estimated uplift area using a regression line. We systematically applied those methods for two cases of previous large earthquakes: the 1952 Tokachi-oki earthquake (Mw8.2) and the 1968 Tokachi-oki earthquake (Mw8.1). The locations of the large computed uplift areas of the earthquakes were well defined by the estimated ones. The estimated magnitudes of the 1952 and 1968 Tokachi-oki earthquakes from the estimated uplift area were 8.2 and 7.9, respectively; they are almost consistent with the moment magnitudes derived from the source models. Those results indicate that the tsunami source estimation method developed in this study can be used for near-real time tsunami forecasts.
  • Yuichiro Tanioka, Aditya Riadi Gusman
    Physics of the Earth and Planetary Interiors 283 82 - 91 0031-9201 2018/10 [Refereed][Not invited]
     
    © 2018 The Authors An approach for forecasting near-field tsunami inundation was developed by combining two methods. The first method computes tsunami by assimilating pressure data observed at numerous ocean bottom sensors without tsunami source information, and the second method forecasts near-field tsunami inundation by selecting a site-specific scenario from a precomputed tsunami inundation database. In order to evaluate the validity of this combined method, we performed a synthetic forecast test for the 2011 Tohoku-oki tsunami along the Pacific coast in Japan. A tsunami computation test performed using the assimilation of synthetic pressure data reveals that the method reproduced well the tsunami field for the 2011 Tohoku-oki tsunami. A synthetic near-field tsunami inundation forecast at four sites, Kamaishi, Rikuzentakata, Minamisanriku, and the Sendai Plain for the 2011 Tohoku-oki tsunami also worked. The results indicate that an accurate tsunami inundation forecast method by this combined approach using pressure data from numerous ocean bottom sensors is now available.
  • Yusuke Yamanaka, Yuichiro Tanioka
    Geophysical Journal International 214 (3) 1937 - 1946 0956-540X 2018/09/01 [Refereed][Not invited]
     
    © The Author(s) 2018. The megathrust earthquake that occurred along the Nazca Plate, near the coasts of Colombia and Ecuador in 1906, induced a large tsunami that propagated over the Pacific Ocean. The tsunami arrived in countries very far from the source region, including the United States and Japan. Part of the land covered by railroad tracks in Hilo Bay, Hawaii, United States, was inundated during the tsunami. The tsunami reached a height of several tens of centimetres in other regions of Hawaii, while residents in Hilo witnessed a height of 3.6 m in the bay. This study aimed to estimate the large amplification and inundation mechanisms of the 1906 Colombia-Ecuador tsunami in Hilo Bay, based on a detailed numerical simulation. First, available tsunami observation data were carefully examined and compared with the results of previous studies. The results indicate a maximum inundation height due to the tsunami in Hilo Bay ranging from 1.1 to 1.8 m. Next, a tsunami inundation simulation was performed under varying conditions, such as energy loss by bottom friction and tide level change, using an earthquake source model. The simulated results were consistent with the observation in terms of the inundation height and indicate that bay-scale resonance occurred in Hilo Bay. Furthermore, waves amplified by resonance were more significant than the primary wave. It can therefore be concluded that bay-scale resonance enhanced the tsunami inundation in Hilo Bay. These new results show that the tsunami magnitude of 8.7, estimated in a previous study, is an overestimation. Instead, the results suggest a lower tsunami magnitude of 8.4, which is consistent with the moment magnitude obtained from the earthquake source model.
  • Alexander B. Rabinovich, Hermann M. Fritz, Yuichiro Tanioka, Eric L. Geist
    Pure and Applied Geophysics 175 (4) 1231 - 1237 0033-4553 2018/04 [Refereed][Not invited]
     
    © 2018, Springer International Publishing AG, part of Springer Nature. Twenty papers on the study of tsunamis are included in Volume III of the PAGEOPH topical issue “Global Tsunami Science: Past and Future”. Volume I of this topical issue was published as PAGEOPH, vol. 173, No. 12, 2016 and Volume II as PAGEOPH, vol. 174, No. 8, 2017. Two papers in Volume III focus on specific details of the 2009 Samoa and the 1923 northern Kamchatka tsunamis; they are followed by three papers related to tsunami hazard assessment for three different regions of the world oceans: South Africa, Pacific coast of Mexico and the northwestern part of the Indian Ocean. The next six papers are on various aspects of tsunami hydrodynamics and numerical modelling, including tsunami edge waves, resonant behaviour of compressible water layer during tsunamigenic earthquakes, dispersive properties of seismic and volcanically generated tsunami waves, tsunami runup on a vertical wall and influence of earthquake rupture velocity on maximum tsunami runup. Four papers discuss problems of tsunami warning and real-time forecasting for Central America, the Mediterranean coast of France, the coast of Peru, and some general problems regarding the optimum use of the DART buoy network for effective real-time tsunami warning in the Pacific Ocean. Two papers describe historical and paleotsunami studies in the Russian Far East. The final set of three papers importantly investigates tsunamis generated by non-seismic sources: asteroid airburst and meteorological disturbances. Collectively, this volume highlights contemporary trends in global tsunami research, both fundamental and applied toward hazard assessment and mitigation.
  • Yuichiro Tanioka, Amilcar Geovanny Cabrera Ramirez, Yusuke Yamanaka
    Pure and Applied Geophysics 175 (4) 1363 - 1370 0033-4553 2018/04 [Refereed][Not invited]
     
    © 2018, The Author(s). The 2016 El Salvador–Nicaragua outer-rise earthquake (Mw 6.9) generated a small tsunami observed at the ocean bottom pressure sensor, DART 32411, in the Pacific Ocean off Central America. The dispersive observed tsunami is well simulated using the linear Boussinesq equations. From the dispersive character of tsunami waveform, the fault length and width of the outer-rise event is estimated to be 30 and 15 km, respectively. The estimated seismic moment of 3.16 × 1019 Nm is the same as the estimation in the Global CMT catalog. The dispersive character of the tsunami in the deep ocean caused by the 2016 outer-rise El Salvador–Nicaragua earthquake could constrain the fault size and the slip amount or the seismic moment of the event.
  • Yuichiro Tanioka
    Pure and Applied Geophysics 175 (2) 721 - 729 0033-4553 2018/02/01 [Refereed][Not invited]
     
    © 2017, The Author(s). A new method was developed to reproduce the tsunami height distribution in and around the source area, at a certain time, from a large number of ocean bottom pressure sensors, without information on an earthquake source. A dense cabled observation network called S-NET, which consists of 150 ocean bottom pressure sensors, was installed recently along a wide portion of the seafloor off Kanto, Tohoku, and Hokkaido in Japan. However, in the source area, the ocean bottom pressure sensors cannot observe directly an initial ocean surface displacement. Therefore, we developed the new method. The method was tested and functioned well for a synthetic tsunami from a simple rectangular fault with an ocean bottom pressure sensor network using 10 arc-min, or 20 km, intervals. For a test case that is more realistic, ocean bottom pressure sensors with 15 arc-min intervals along the north–south direction and sensors with 30 arc-min intervals along the east–west direction were used. In the test case, the method also functioned well enough to reproduce the tsunami height field in general. These results indicated that the method could be used for tsunami early warning by estimating the tsunami height field just after a great earthquake without the need for earthquake source information.
  • Kawakami Gentaro, Ioki Kei, Yanagisawa Hideaki, Tanioka Yuichiro, Kase Yoshihiro, Nishina Kenji, Hirose Wataru, Koyasu Hiromichi, Urabe Atsushi
    Annual Meeting of the Geological Society of Japan 一般社団法人 日本地質学会 2018 83 - 83 1348-3935 2018
  • Tanioka Yuichiro
    Annual Meeting of the Geological Society of Japan 一般社団法人 日本地質学会 2018 74 - 74 1348-3935 2018
  • SUZUKI Takayuki, NISHIOKA Yoichi, MURASHIMA Yoichi, TAKAYAMA Jumpei, TANIOKA Yuichiro, YAMASHITA Toshihiko
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 土木学会 74 (2) I_439 - 444 1884-2399 2018 
     It necessary to set relatively high frequency tsunami for preservation of coastal facilities.We called this tsunami "tsunami for designing". However, tsunami was occur less frequently, and different characteristic, history by each region. Suzuki et al., tryed to set "tsunami for designing" that focus to average occurence interval of earthquake by Headquarters for Earthquake Research Promotion, proposed the method that used comulative incidence rate of tsunami. In this study, targets Japan Sea side of Hokkaido that has be character that considerably lower frequency of earthquake than ocean-trench earthquake, and have be many active fault. We verificated applicability of this method on Japan Sea side of Hokkaido.
  • Yusuke Yamanaka, Yuichiro Tanioka, Takahiro Shiina
    Earth, Planets and Space 69 (1) 1343-8832 2017/12/01 [Not refereed][Not invited]
     
    © 2017, The Author(s). The 1906 Colombia–Ecuador earthquake induced both strong seismic motions and a tsunami, the most destructive earthquake in the history of the Colombia–Ecuador subduction zone. The tsunami propagated across the Pacific Ocean, and its waveforms were observed at tide gauge stations in countries including Panama, Japan, and the USA. This study conducted slip inverse analysis for the 1906 earthquake using these waveforms. A digital dataset of observed tsunami waveforms at the Naos Island (Panama) and Honolulu (USA) tide gauge stations, where the tsunami was clearly observed, was first produced by consulting documents. Next, the two waveforms were applied in an inverse analysis as the target waveform. The results of this analysis indicated that the moment magnitude of the 1906 earthquake ranged from 8.3 to 8.6. Moreover, the dominant slip occurred in the northern part of the assumed source region near the coast of Colombia, where little significant seismicity has occurred, rather than in the southern part. The results also indicated that the source area, with significant slip, covered a long distance, including the southern, central, and northern parts of the region.[Figure not available: see fulltext.].
  • Takuji Yamada, Yu Saito, Yuichiro Tanioka, Jun Kawahara
    PROGRESS IN EARTH AND PLANETARY SCIENCE 4 (38) 2197-4284 2017/12 [Refereed][Not invited]
     
    We show that the spatial heterogeneity in the coseismic displacement of large earthquakes likely reflects the spatial characteristics of the frictional properties and that it can be inferred from the stress drop of moderate-sized earthquakes. We analyzed stress drops of 686 earthquakes with magnitudes of 4.0 to 5.0 off the south-east of Hokkaido, Japan, and investigated the spatial heterogeneity between the difference of shear strength and dynamic stress level on the Pacific Plate. We deconvolved observed P and S waves with those of collocated small earthquakes and derived the source effect of the earthquakes. We then estimated the corner frequencies of the earthquakes and calculated stress drops using a circular fault model. The values of stress drops showed a spatial pattern consistent with slip distributions of historical large earthquakes. Earthquakes that occurred in the area with a large coseismic slip during the 1968 Tokachi-oki (M (W) 8.2) and the 2003 Tokachi-oki (M (W) 8.0) earthquakes had large values of stress drop, whereas earthquakes in the afterslip area of the 2003 Tokachi-oki earthquake showed smaller values. In addition, an area between coseismic ruptures of the 1973 Nemuro-oki (M (W) 7.8) and the 2003 Tokachi-oki earthquakes had a large value of stress drop. Ruptures occurred in this area during the 1952 Tokachi-oki earthquake (M (W) 8.1), and the area acted as a barrier during the 2003 Tokachi-oki earthquake. These facts suggest that the frictional properties of the plate interface show little temporal change, and their spatial pattern can be monitored by stress drops of moderate-sized earthquakes. The spatial heterogeneity provides important information for estimating the slip pattern of a future large earthquake and discussing a policy for disaster mitigation, especially for regions in which slip patterns of historical large earthquakes are unclear.
  • Alexander B. Rabinovich, Hermann M. Fritz, Yuichiro Tanioka, Eric L. Geist
    PURE AND APPLIED GEOPHYSICS 174 (8) 2883 - 2889 0033-4553 2017/08 [Refereed][Not invited]
     
    Twenty-two papers on the study of tsunamis are included in Volume II of the PAGEOPH topical issue "Global Tsunami Science: Past and Future". Volume I of this topical issue was published as PAGEOPH, vol. 173, No. 12, 2016 (Eds., E. L. Geist, H. M. Fritz, A. B. Rabinovich, and Y. Tanioka). Three papers in Volume II focus on details of the 2011 and 2016 tsunami-generating earthquakes offshore of Tohoku, Japan. The next six papers describe important case studies and observations of recent and historical events. Four papers related to tsunami hazard assessment are followed by three papers on tsunami hydrodynamics and numerical modelling. Three papers discuss problems of tsunami warning and real-time forecasting. The final set of three papers importantly investigates tsunamis generated by non-seismic sources: volcanic explosions, landslides, and meteorological disturbances. Collectively, this volume highlights contemporary trends in global tsunami research, both fundamental and applied toward hazard assessment and mitigation.
  • Aditya Riadi Gusman, Kenji Satake, Masanao Shinohara, Shin'ichi Sakai, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 174 (8) 2925 - 2943 0033-4553 2017/08 [Refereed][Not invited]
     
    The 2016 Fukushima normal-faulting earthquake (Mjma 7.4) occurred 40 km off the coast of Fukushima within the upper crust. The earthquake generated a moderate tsunami which was recorded by coastal tide gauges and offshore pressure gauges. First, the sensitivity of tsunami waveforms to fault dimensions and depths was examined and the best size and depth were determined. Tsunami waveforms computed based on four available focal mechanisms showed that a simple fault striking northeast-southwest and dipping southeast (strike = 45 degrees, dip = 41 degrees, rake = -95 degrees) yielded the best fit to the observed waveforms. This fault geometry was then used in a tsunami waveform inversion to estimate the fault slip distribution. A large slip of 3.5 m was located near the surface and the major slip region covered an area of 20 km x 20 km. The seismic moment, calculated assuming a rigidity of 2.7 x 10(10) N/m(2) was 3.70 x 10(19) Nm, equivalent to Mw = 7.0. This is slightly larger than the moments from the moment tensor solutions (Mw 6.9). Large secondary tsunami peaks arrived approximately an hour after clear initial peaks were recorded by the offshore pressure gauges and the Sendai and Ofunato tide gauges. Our tsunami propagation model suggests that the large secondary tsunami signals were from tsunami waves reflected off the Fukushima coast. A rather large tsunami amplitude of similar to 75 cm at Kuji, about 300 km north of the source, was comparable to those recorded at stations located much closer to the epicenter, such as Soma and Onahama. Tsunami simulations and ray tracing for both real and artificial bathymetry indicate that a significant portion of the tsunami wave was refracted to the coast located around Kuji and Miyako due to bathymetry effects.
  • Yusuke Yamanaka, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 174 (8) 3275 - 3291 0033-4553 2017/08 [Refereed][Not invited]
     
    Large sector collapses and landslides have the potential to cause significant disasters. Estimating the topography and conditions, such as volume, before the collapse is thus important for analyzing the behavior of moving collapsed material and hazard risks. This study considers three historical volcanic sector collapses in Japan that caused tsunamis: the collapses of the Komagatake Volcano in 1640, Oshima-Oshima Island in 1741, and Unzen-Mayuyama Volcano in 1792. Numerical simulations of the tsunamis generated by each event were first carried out based on assumed collapse scenarios. The primary objective of this study is to present conditions related to the topography before the events based on inverse models of the topography from those results and tsunami survey data. The Oshima-Oshima Tsunami, which is the subject of many previous studies, was first simulated to validate the model accuracy and evaluate how run-up heights changed during the simulation as the topographic conditions changed. The run-up height was especially sensitive to the collapsed volume and frictional acceleration affecting the collapsed material; however, the observed run-up heights could be reproduced with high accuracy using proper conditions of frictional acceleration for the scenarios, even if they were not exact. A minimum requirement for the collapsed volume to generate the observed run-up height was introduced and quantitatively evaluated using the results of numerical tsunami simulations. The minimum volumes of the collapses of the Komagatake and Unzen-Mayuyama volcanoes were estimated to be approximately 1.2 and 0.3 km(3), respectively.
  • Yuichiro Tanioka, Greyving Jose Arguello Miranda, Aditya Riadi Gusman, Yushiro Fujii
    PURE AND APPLIED GEOPHYSICS 174 (8) 3237 - 3248 0033-4553 2017/08 [Refereed][Not invited]
     
    Large earthquakes, such as the Mw 7.7 1992 Nicaragua earthquake, have occurred off the Pacific coasts of El Salvador and Nicaragua in Central America and have generated distractive tsunamis along these coasts. It is necessary to determine appropriate fault models before large tsunamis hit the coast. In this study, first, fault parameters were estimated from the W-phase inversion, and then an appropriate fault model was determined from the fault parameters and scaling relationships with a depth dependent rigidity. The method was tested for four large earthquakes, the 1992 Nicaragua tsunami earthquake (Mw7.7), the 2001 El Salvador earthquake (Mw7.7), the 2004 El Astillero earthquake (Mw7.0), and the 2012 El Salvador-Nicaragua earthquake (Mw7.3), which occurred off El Salvador and Nicaragua in Central America. The tsunami numerical simulations were carried out from the determined fault models. We found that the observed tsunami heights, run-up heights, and inundation areas were reasonably well explained by the computed ones. Therefore, our method for tsunami early warning purpose should work to estimate a fault model which reproduces tsunami heights near the coast of El Salvador and Nicaragua due to large earthquakes in the subduction zone.
  • 谷岡勇市郎, 椎名高裕
    地震ジャーナル 地震予知総合研究振興会 (63) 40‐44 - 44 0912-5779 2017/06/20 [Not refereed][Not invited]
  • SUZUKI Takayuki, NISHIOKA Yoichi, MURASHIMA Yoichi, TAKAYAMA Jumpei, TANIOKA Yuichiro, YAMASHITA Toshihiko
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_1591 - I_1596 1884-2399 2017 
     It is necessary to set the design tsunami for the maintenance of coastal protection facilities. However, the setting of this tsunami does not have a clear standard. Therefore we calculated cumulative occurrence probability that forcused on occurrence probability of the earthquake by the Headquartere for Earthquake Research Promotion , and we suggested the method with cumulative occurrence probability in this study. Target areas were between Rausu-cho and Fukushima-cho in Hokkaido Pacific coast.
  • Kawakami Gentaro, Ioki Kei, Yanagisawa Hideaki, Kase Yoshihiro, Nishina Kenji, Koyasu Hiromichi, Tanioka Yuichiro
    Annual Meeting of the Geological Society of Japan 一般社団法人 日本地質学会 2017 272 - 272 1348-3935 2017 
    [Program canceled for typhoon] Program canceled for typhoon. However, This abstract is quotable and viewable on PDF.
  • Kei Ioki, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 173 (12) 4179 - 4187 0033-4553 2016/12 [Refereed][Not invited]
     
    The 1969 and 1975 great Kurile earthquakes occurred along the Kurile trench. Tsunamis generated by these earthquakes were observed at tide gauge stations around the coasts of the Okhotsk Sea and Pacific Ocean. To understand rupture process of the 1969 and 1975 earthquakes, slip distributions of the 1969 and 1975 events were estimated using tsunami waveform inversion technique. Seismic moments estimated from slip distributions of the 1969 and 1975 earthquakes were 1.1 x 1021 Nm (M (w) 8.0) and 0.6 x 1021 Nm (M (w) 7.8), respectively. The 1973 Nemuro-Oki earthquake occurred at the plate interface adjacent to that ruptured by the 1969 Kurile earthquake. The 1975 Shikotan earthquake occurred in a shallow region of the plate interface where was not ruptured by the 1969 Kurile earthquake. Further, like a sequence of the 1969 and 1975 earthquakes, it is possible that a great earthquake may occur in a shallow part of the plate interface a few years after a great earthquake that occurs in a deeper part of the same region along the trench.
  • Eric L. Geist, Hermann M. Fritz, Alexander B. Rabinovich, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 173 (12) 3663 - 3669 0033-4553 2016/12 [Refereed][Not invited]
     
    Twenty-five papers on the study of tsunamis are included in Volume I of the PAGEOPH topical issue "Global Tsunami Science: Past and Future". Six papers examine various aspects of tsunami probability and uncertainty analysis related to hazard assessment. Three papers relate to deterministic hazard and risk assessment. Five more papers present new methods for tsunami warning and detection. Six papers describe new methods for modeling tsunami hydrodynamics. Two papers investigate tsunamis generated by non-seismic sources: landslides and meteorological disturbances. The final three papers describe important case studies of recent and historical events. Collectively, this volume highlights contemporary trends in global tsunami research, both fundamental and applied toward hazard assessment and mitigation.
  • Kei Ioki, Yuichiro Tanioka
    EARTH AND PLANETARY SCIENCE LETTERS 433 133 - 138 0012-821X 2016/01 [Refereed][Not invited]
     
    Paleotsunami researches revealed that a great earthquake occurred off eastern Hokkaido, Japan and generated a large tsunami in the 17th century. Tsunami deposits from this event have been found at far inland from the Pacific coast in eastern Hokkaido. Previous study estimated the fault model of the 17th century great earthquake by comparing locations of lowland tsunami deposits and computed tsunami inundation areas. Tsunami deposits were also traced at high cliff near the coast as high as 18 m above the sea level. Recent paleotsunami study also traced tsunami deposits at other high cliffs along the Pacific coast. The fault model estimated from previous study cannot explain the tsunami deposit data at high cliffs near the coast. In this study, we estimated the fault model of the 17th century great earthquake to explain both lowland widespread tsunami deposit areas and tsunami deposit data at high cliffs near the coast. We found that distributions of lowland tsunami deposits were mainly explained by wide rupture area at the plate interface in Tokachi-Oki segment and Nemuro-Oki segment. Tsunami deposits at high cliff near the coast were mainly explained by very large slip of 25 m at the shallow part of the plate interface near the trench in those segments. The total seismic moment of the 17th century great earthquake was calculated to be 1.7 x 10(22) N m (M-w 8.8). The 2011 great Tohoku earthquake ruptured large area off Tohoku and very large slip amount was found at the shallow part of the plate interface near the trench. The 17th century great earthquake had the same characteristics as the 2011 great Tohoku earthquake. (C) 2015 Elsevier B.V. All Lights reserved.
  • Ichiyanagi, M, H. Takahashi, T. Yamaguchi, R. Azuma, T. Yamada, M. Ohzono, A. Shinjo, M. Kasahara, Y. Tanioka
    Geophys. Bull. Hokkaido Univ. 北海道大学大学院理学研究院 78 (78) 37 - 51 0439-3503 2015/03 [Not refereed][Not invited]
  • Aditya Riadi Gusman, Yuichiro Tanioka
    Advances in Natural and Technological Hazards Research 44 157 - 177 2213-6959 2015 [Refereed][Not invited]
     
    An algorithm called NearTIF, designed to produce tsunami inundation maps of near-field sites before the actual tsunami hits the shore, was previously developed by the authors. This algorithm relies on a database of precomputed tsunami waveforms at several near-shore locations and tsunami inundation maps from various earthquake fault models. In the event of a great earthquake, tsunami waveforms at the above mentioned near-shore locations are computed on the basis of real-time observation data by use of linear long-wave equations. Simulating these tsunami waveforms takes only 1-3 min on a common personal computer, so the realistic offshore tsunami waveforms can be forecasted. The offshore real-time simulated tsunami waveforms are then compared with precomputed tsunami waveforms in a database to select the site-specific best fault model and the corresponding tsunami inundation map. The best tsunami inundation map is then used as the tsunami inundation forecast. We evaluated the effectiveness of this algorithm in the real world by carrying out a tsunami evacuation drill in Kushiro City, Hokkaido, Japan, involving the city residents. The drill started with the announcement of a tsunami warning, to evacuate the residents to the nearest evacuation building. Approximately 10 min after the announcement, the tsunami inundation forecast map was given to the participants in the drill. The participants found that the use of the tsunami inundation forecast map produced by NearTIF was effective in helping them make better decisions with high confidence during the tsunami evacuation drill. The NearTIF algorithm is recommended for use as part of the reconstruction policy by local authorities to improve the evacuation efficiency, particularly in tsunami-prone areas.
  • Aditya Riadi Gusman, Yuichiro Tanioka, Breanyn T. MacInnes, Hiroaki Tsushima
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 119 (11) 8186 - 8206 2169-9313 2014/11 [Refereed][Not invited]
     
    Existing tsunami early warning systems in the world can give either one or a combination of estimated tsunami arrival times, heights, or qualitative tsunami forecasts before the tsunami hits near-field coastlines. A future tsunami early warning system should be able to provide a reliable near-field tsunami inundation forecast on high-resolution topography within a short time period. Here we describe a new methodology for near-field tsunami inundation forecasting. In this method, a precomputed tsunami inundation and precomputed tsunami waveform database is required. After information about a tsunami source is estimated, tsunami waveforms at nearshore points can be simulated in real time. A scenario that gives the most similar tsunami waveforms is selected as the site-specific best scenario and the tsunami inundation from that scenario is selected as the tsunami inundation forecast. To test the algorithm, tsunami inundation along the Sanriku Coast is forecasted by using source models for the 2011 Tohoku earthquake estimated from GPS, W phase, or offshore tsunami waveform data. The forecasting algorithm is capable of providing a tsunami inundation forecast that is similar to that obtained by numerical forward modeling but with remarkably smaller CPU time. The time required to forecast tsunami inundation in coastal sites from the Sendai Plain to Miyako City is approximately 3min after information about the tsunami source is obtained. We found that the tsunami inundation forecasts from the 5min GPS, 5minW phase, 10minW phase fault models, and 35min tsunami source model are all reliable for tsunami early warning purposes and quantitatively match the observations well, although the latter model gives tsunami forecasts with highest overall accuracy. The required times to obtain tsunami forecast from the above four models are 8min, 9min, 14min, and 39min after the earthquake, respectively, or in other words 3min after receiving the source model. This method can be useful in developing future tsunami forecasting systems with a capability of providing tsunami inundation forecasts for locations near the tsunami source area.
  • Aditya Riadi Gusman, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 171 (7) 1409 - 1422 0033-4553 2014/07 [Refereed][Not invited]
     
    Centroid moment tensor solutions for the 2011 Tohoku earthquake are determined by W phase inversions using 5 and 10 min data recorded by the Full Range Seismograph Network of Japan (F-net). By a scaling relation of moment magnitude to rupture area and an assumption of rigidity of 4 x 10(10) N m(-2), simple rectangular earthquake fault models are estimated from the solutions. Tsunami inundations in the Sendai Plain, Minamisanriku, Rikuzentakata, and Taro are simulated using the estimated fault models. Then the simulated tsunami inundation area and heights are compared with the observations. Even the simulated tsunami heights and inundations from the W phase solution that used only 5 min data are considerably similar to the observations. The results are improved when using 10 min of W phase data. These show that the W phase solutions are reliable to be used for tsunami inundation modeling. Furthermore, the technique that combines W phase inversion and tsunami inundation modeling can produce results that have sufficient accuracy for tsunami early warning purposes.
  • Yuichiro Tanioka, Aditya Riadi Gusman, Kei Ioki, Yugo Nakamura
    Journal of Disaster Research 9 358 - 364 1881-2473 2014/01/01 [Not refereed][Not invited]
     
    Paleotsunami studies have shown that several large tsunamis hit the Pacific coast. Many tsunami deposit data were available for the 17thcentury tsunami. The most recent tsunami deposit study in 2013 indicated that the large slip of about 25 m along the plate interface near the Kurile trench would be necessary and the seismic moment of this 17thcentury earthquake was 1.7 × 1022Nm. If a great earthquake like the 17thcentury earthquake occurs off the Pacific coast of Hokkaido, the devastating disaster along the coast is expected. To minimize the tsunami disaster, a development of the real-time forecast of a tsunami inundation area is necessary. Estimating a tsunami inundation area requires tsunami numerical simulation with a very fine grid system of less than 1 arcsecond. There is not enough time to compute the tsunami inundation area after a large earthquake occurs. In this study, we develop a real-time tsunami inundation forecast method using a database including many tsunami inundation areas previously computed using various fault models. After great earthquakes, tsunamis are computed using linear long-wave equations for fault models estimated in real time. Simulating such tsunamis takes only 1-3 minutes on a typical PC, so it is potentially useful for forecasting tsunamis. Tsunami inundation areas computed numerically using various fault models and tsunami waveforms at several locations near the inundation area are stored in a database. Those computed tsunami waveforms are used to choose the most appropriate tsunami inundation area by comparing them to the tsunami wave- forms computed in real time. This method is tested at Kushiro, a city in Hokkaido. We found that the method worked well enough to forecast the Kushiro's tsunami inundation area.
  • Kenji Satake, Yuichi Nishimura, Purna Sulastya Putra, Aditya Riadi Gusman, Haris Sunendar, Yushiro Fujii, Yuichiro Tanioka, Hamzah Latief, Eko Yulianto
    PURE AND APPLIED GEOPHYSICS 170 (9-10) 1567 - 1582 0033-4553 2013/09 [Refereed][Not invited]
     
    The 2010 Mentawai earthquake (magnitude 7.7) generated a destructive tsunami that caused more than 500 casualties in the Mentawai Islands, west of Sumatra, Indonesia. Seismological analyses indicate that this earthquake was an unusual "tsunami earthquake," which produces much larger tsunamis than expected from the seismic magnitude. We carried out a field survey to measure tsunami heights and inundation distances, an inversion of tsunami waveforms to estimate the slip distribution on the fault, and inundation modeling to compare the measured and simulated tsunami heights. The measured tsunami heights at eight locations on the west coasts of North and South Pagai Island ranged from 2.5 to 9.3 m, but were mostly in the 4-7 m range. At three villages, the tsunami inundation extended more than 300 m. Interviews of local residents indicated that the earthquake ground shaking was less intense than during previous large earthquakes and did not cause any damage. Inversion of tsunami waveforms recorded at nine coastal tide gauges, a nearby GPS buoy, and a DART station indicated a large slip (maximum 6.1 m) on a shallower part of the fault near the trench axis, a distribution similar to other tsunami earthquakes. The total seismic moment estimated from tsunami waveform inversion was 1.0 x 10(21) Nm, which corresponded to M-w 7.9. Computed coastal tsunami heights from this tsunami source model using linear equations are similar to the measured tsunami heights. The inundation heights computed by using detailed bathymetry and topography data and nonlinear equations including inundation were smaller than the measured ones. This may have been partly due to the limited resolution and accuracy of publically available bathymetry and topography data. One-dimensional run-up computations using our surveyed topography profiles showed that the computed heights were roughly similar to the measured ones.
  • Breanyn T. MacInnes, Aditya Riadi Gusman, Randall J. LeVeque, Yuichiro Tanioka
    BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 103 (2B) 1256 - 1274 0037-1106 2013/05 [Refereed][Not invited]
     
    Selection of the earthquake source used in tsunami models of the 2011 Tohoku event affects the simulated tsunami waveform across the near field. Different earthquake sources, based on inversions of seismic waveforms, tsunami waveforms, and Global Positioning System (GPS) data, give distinguishable patterns of simulated tsunami heights in many locations in Tohoku and at near-field Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys. We compared 10 sources proposed by different research groups using the GeoClaw code to simulate the resulting tsunami. Several simulations accurately reproduced observations at simulation sites with high grid resolution. Many earthquake sources produced results within 20% difference from the observations between 38 degrees and 39 degrees N, including realistic inundation on the Sendai plain, reflecting a common reliance on large initial seafloor uplift around 38 degrees N (+/- 0.5 degrees), 143.25 degrees E (+/- 0.75 degrees). As might be expected, DART data was better reproduced by sources created by inversion techniques that incorporated DART data in the inversion. Most of the earthquake sources tested at sites with high grid resolution were unable to reproduce the magnitude of runup north of 39 degrees N, indicating that an additional source of tsunamigenic energy, not present in most source models, is needed to explain these observations.
  • Yuichiro Tanioka, Kenji Satake, Kenji Hirata
    Volcanism and Subduction: The Kamchatka Region 145 - 152 2013/03/19 [Refereed][Not invited]
     
    Recurrent large earthquakes in the southernmost part of the Kurile-Kamchatka subduction zone were studied. Previous studies have indicated that the 1994 Sanriku-oki earthquake (Mw 7.8) ruptured only the southern part of the rupture area of the 1968 Tokachi-oki earthquake (Mw 8.2), and left the main rupture interface of the 1968 earthquake intact. Also, the 2003 Tokachi-oki earthquake (Mw 8.1) did not rupture the eastern part of the rupture area of the 1952 Tokachioki earthquake (Mw 8.2). The rupture processes of the 1973 and 1894 Nemuro-oki earthquakes were studied through tsunami waveform analyses. The rupture of the 1973 Nemuro-oki earthquake was concentrated on the plate interface off Nemuro, Hokkaido, and the seismic moment was estimated to be 6.5 × 1020 Nm (Mw 7.8). The 1894 Nemuro-oki earthquake ruptured much larger area than that of the 1973 Nemuro-oki earthquake. The fault length of the 1894 earthquake was about 200 km, and the seismic moment was 28.8 × 1020 Nm (Mw 8.3). In this subduction zone, none of three sets of recent recurrent large earthquakes, the 1968 Tokachi and 1994 Sanriku-oki earthquakes, the 1952 and 2003 Tokachi-oki earthquakes, and the 1894 and 1973 Nemuro-oki earthquakes, have the same rupture processes. Variable rupture patterns of large recurrent earthquakes make it difficult to estimate the source processes of future large earthquakes in this subduction zone. These non-regular recurrences also suggest that, in addition to invariant geometric and material heterogeneities, the dynamic stress heterogeneities are seen to be important for understanding large earthquake complexity in this subduction zone.
  • Aditya Riadi Gusman, Mitsuteru Fukuoka, Yuichiro Tanioka, Shin'ichi Sakai
    GEOPHYSICAL RESEARCH LETTERS 40 (3) 497 - 500 0094-8276 2013/02 [Refereed][Not invited]
     
    The slip distribution of the largest foreshock that occurred 2 days before the mainshock of the 2011 Tohoku earthquake is estimated by tsunami waveform inversion. The major slip region was located on the down-dip side of the hypocenter, and the slip amounts ranged from 0.6 to 1.5 m. By assuming the rigidity of 4 x 10(10) N m(-2), the seismic moment calculated from the slip distribution is 1.2 x 10(20) N m (Mw 7.3). The slip distribution suggests that the largest foreshock did not rupture the plate interface where the dynamic rupture of the mainshock was initiated. The largest foreshock increased the Coulomb stress (1.6-4.5 bars) on the plate interface around the hypocenter of the mainshock. This indicates that the 2011 Tohoku earthquake was brought closer to failure by the largest foreshock. Citation: Gusman, A. R., M. Fukuoka, Y. Tanioka, and S.'i. Sakai (2013), Effect of the largest foreshock (Mw 7.3) on triggering the 2011 Tohoku earthquake (Mw 9.0), Geophys. Res. Lett., 40, 497-500, doi:10.1002/grl.50153.
  • Aditya Riadi Gusman, Yuichiro Tanioka, Shinichi Sakai, Hiroaki Tsushima
    EARTH AND PLANETARY SCIENCE LETTERS 341 234 - 242 0012-821X 2012/08 [Refereed][Not invited]
     
    The slip distribution of the 11 March 2011 Tohoku earthquake is inferred from tsunami waveforms, GPS data, and seafloor crustal deformation data. The major slip region extends all the way to the trench, and the large slip area extends 300 km long and 160 km wide. The largest slip of 44 m is located up-dip of the hypocenter. The large slip amount, about 41 m, ruptured the plate interface near the trench. The seismic moment calculated from the estimated slip distribution is 5.5 x 10(22) N m (Mw 9.1). The large tsunami due to the 2011 Tohoku earthquake is generated from those large slip areas near the trench. The additional uplift at the sedimentary wedge as suggested for the 1896 Sanriku earthquake may have occurred during the 2011 Tohoku earthquake, too. (C) 2012 Elsevier B.V. All rights reserved.
  • Yoshihiro Kakinami, Masashi Kamogawa, Yuichiro Tanioka, Shigeto Watanabe, Aditya Riadi Gusman, Jann-Yenq Liu, Yasuyuki Watanabe, Toru Mogi
    GEOPHYSICAL RESEARCH LETTERS 39 0094-8276 2012/06 [Refereed][Not invited]
     
    Traveling ionospheric disturbances generated by an epicentral ground/sea surface motion, ionospheric disturbances associated with Rayleigh-waves as well as post-seismic 4-minute monoperiodic atmospheric resonances and other-period atmospheric oscillations have been observed in large earthquakes. In addition, a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content (TEC) in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area. The tsunamigenic ionospheric hole detected by the TEC measurement with Global Position System (GPS) was found in the 2011 M9.0 off the Pacific coast of Tohoku, the 2010 M8.8 Chile, and the 2004 M9.1 Sumatra earthquakes. This occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter-scale downwelling of sea surface at the tsunami source area, and is highly depleted due to the chemical processes. Citation: Kakinami, Y., M. Kamogawa, Y. Tanioka, S. Watanabe, A.R. Gusman, J.-Y. Liu, Y. Watanabe, and T. Mogi (2012), Tsunamigenic ionospheric hole, Geophys. Res. Lett., 39, L00G27, doi: 10.1029/2011GL050159.
  • Hiroaki Tsushima, Ryota Hino, Yuichiro Tanioka, Fumihiko Imamura, Hiromi Fujimoto
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 117 2169-9313 2012/03 [Refereed][Not invited]
     
    We propose a method of tsunami waveform inversion to accurately estimate a tsunami source by incorporating the effect of permanent seafloor deformation recorded by ocean-bottom pressure gauges (OBPGs) within the source region. We developed a general expression of water-depth fluctuation recorded at an OBPG following seafloor deformation of arbitrary spatiotemporal distribution. By assuming that coseismic rupture propagates with infinite velocity, the general expression can be reduced to an equation relating observed OBPG waveforms to initial sea-surface displacement at the source by using a Green's function consisting of two terms: the Green's function used in regular tsunami inversion and a correction term to account for water-depth change in response to permanent seafloor deformation. By using the two-term Green's functions, the effect of seafloor deformation can be taken into account in tsunami source estimation. We applied the revised inversion method to observations of coseismic seafloor deformation and tsunami during the 2003 Tokachi-oki earthquake (M-w 8.3) at two OBPG stations near the Kuril Trench. The tsunami source model we estimated is consistent with models previously derived using various other geophysical data sets. Furthermore, the coastal tsunami waveforms we modeled match the observed tsunami well. Forecasts of tsunami arrival times and first peak amplitudes by our method can be obtained 20 min after an earthquake, and can be provided to the coastal communities nearest to the source with a lead time of similar to 10 min.
  • Aditya Riadi Gusman, Yuichiro Tanioka, Tomoyuki Takahashi
    EARTH PLANETS AND SPACE 64 (10) 817 - 827 1880-5981 2012 [Refereed][Not invited]
     
    We use a two-dimensional tsunami sediment transport model to study the source of the 2004 earthquake. To test the model behavior, numerical experiment on sediment deposition and erosion is performed using various hypothetical parameters of tsunami wavelength, topographic slope, and sediment supply. The numerical experiment results show that erosion and deposition are strongly influenced by the tsunami wavelength and the topographic slope. The model is used to compute the spatial distribution of tsunami deposit thickness produced by the 2004 Indian Ocean over an actual elevation datasets in the coastal area of Lhok Nga, Banda Aceh, Indonesia. The model produced simulated tsunami deposits that have similar thicknesses with the measured data along a surveyed transect. Then we estimate a simple fault model for the southern portion of the 2004 earthquake using tsunami sediment transport simulations. The simulated tsunami run-up from the fault model is very close to the measured run-up. This result indicates that a source process of a large earthquake that generates a large tsunami has a potential to be estimated using sediment deposit distribution data.
  • Kazuhisa Goto, Yuichiro Tanioka, Yuichi Nishimura, Fumihiko Imamura, Shunichi Koshimura, Giuseppe Mastronuzzi
    EARTH PLANETS AND SPACE 64 (10) 785 - 785 1343-8832 2012 [Refereed][Not invited]
  • Yuichiro Tanioka, Hamzah Latief, Haris Sunendar, Aditya Riadi Gusman, Shunichi Koshimura
    Journal of Disaster Research 7 (1) 19 - 25 1883-8030 2012 [Refereed][Not invited]
     
    Several large earthquakes have recently occurred along the Sumatra-Java subduction zone, the 2004 great Sumatra-Andaman earthquake, the 2005 great Nias earthquake, the 2006 West Java tsunami earthquake, the 2007 great Bengkulu earthquake, and the 2010Mentawai tsunami earthquakes. Serious tsunami disasters were caused by the great underthrust earthquakes which ruptured the plate interface near the trench such as the 2004 Sumatra-Andaman, 2006West Java, 2010Mentawai earthquakes. At Palabuhanratu, maximum tsunami height distribution and inundation areas were computed from expected fault models located near the Java trench. The results shows that the most populated areas of Palabuhanratu would be severely damaged by the expected tsunami caused by the fault model of Mw 8.5. After discussing tsunami disaster mitigation measures with the local government, the result of tsunami inundation area in this study were used to decide tsunami evacuation areas and evacuation routes. The local government also installed tsunami evacuation sign boards near the coast.
  • 北海道における地震津波防災に対する取組と今後の課題
    高橋浩晃, 定池祐季, 谷岡勇市郎
    日本地震学会モノグラフ 1 81 - 85 2012 [Not refereed][Not invited]
  • Subesh Ghimire, Yuichiro Tanioka
    TECTONOPHYSICS 511 (1-2) 1 - 13 0040-1951 2011/10 [Refereed][Not invited]
     
    We investigate spatial distribution of stress along the interplate boundary between Pacific and Okhotsk plates in Tohoku and Hokkaido regions, northern Japan from earthquake focal mechanisms compiled from the National Institute for Earth Science and Disaster Prevention (NIED) of Japan. The interplate boundary in this work is inferred as the surface defining the upper boundary of the double seismic zone (Benioff Zone). To investigate spatial variation in stress field we divide the interplate boundary into 20 km x 20 km subfaults and estimate stress field in each subfault of 10 km thickness. We find clear spatial variation in stress state along the subduction zone of the Pacific plate in northern Japan. Though most of the study area is characterized by trench normal uniaxial compression, in the Hidaka Collision Zone, the signature of collision between the Kurile and Japan arcs is evident in terms of radial compression. Distribution of the angle (psi) between the maximum principal stress direction and the fault normal shows that the large subduction earthquakes have occurred in the region where this angle psi varies between 30 and 45 degrees. However in the case of recent M9.1,2011 Tohoku-Oki earthquake, this correlation is not observed. We further investigate the frictional strength along the interplate boundary. Our results suggest: (1) The fault segments with psi between 30 and 45 degrees are frictionally strong (with friction coefficients between 0.6 and 0.8), (2) The fault segments with psi between 45 and 62 degrees are intermediately strong (with friction coefficients between 0.4 and 0.6), and (3) The fault segments with psi above 62 degrees are weak (with friction coefficients below 0.4). (C) 2011 Elsevier B.V. All rights reserved.
  • Kei Ioki, Yuichiro Tanioka
    PURE AND APPLIED GEOPHYSICS 168 (6-7) 1045 - 1052 0033-4553 2011/06 [Refereed][Not invited]
     
    The 1963 great Kurile earthquake was an underthrust earthquake occurred in the Kurile-Kamchatka subduction zone. The slip distribution of the 1963 earthquake was estimated using 21 tsunami waveforms recorded at tide gauges along the Pacific and Okhotsk Sea coasts. The extended rupture area was divided into 24 subfaults, and the slip on each subfault was determined by the tsunami waveform inversion. The result shows that the largest slip amount of 2.8 m was found at the shallow part and intermediate depth of the rupture area. Large slip amounts were found at the shallow part of the rupture area. The total seismic moment was estimated to be 3.9 x 10(21) Nm (M-w 8.3). The 2006 Kurile earthquake occurred right next to the location of the 1963 earthquake, and no seismic gap exists between the source areas of the 1963 and 2006 earthquakes.
  • 谷岡 勇市郎, 佐竹 健治
    海洋 海洋出版 43 (5) 251 - 258 0916-2011 2011/05 [Not refereed][Not invited]
  • 岡田 正実, 谷岡 勇市郎
    月刊地球 海洋出版 33 (4) 193 - 197 0387-3498 2011/04
  • Hiroaki Tsushima, Kenji Hirata, Yutaka Hayashi, Yuichiro Tanioka, Kazuhiro Kimura, Shin'ichi Sakai, Masanao Shinohara, Toshihiko Kanazawa, Ryota Hino, Kenji Maeda
    EARTH PLANETS AND SPACE 63 (7) 821 - 826 1343-8832 2011 [Refereed][Not invited]
     
    Tsunami heights greater than 4 m were observed at several coastal tide-gauge stations during the tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake (M(w) 9.0), causing thousands of casualties and damaging infrastructure along the Pacific coast of Japan. We retrospectively applied an algorithm of near-field tsunami forecasting to tsunami data that were recorded at various offshore tsunami stations 5-10 min before the tsunami reached the coastal tide-gauge stations nearest to its source. We inverted the waveform data recorded offshore to estimate the distribution of the initial sea-surface height, and then tsunami waveforms were synthesized from the estimated source to forecast tsunami arrival times and amplitudes at coastal tide-gauge stations. As a result of a retrospective application made 20 min after the earthquake, tsunamis with heights of 6-14 m were forecasted at tide-gauge stations nearest to the source where the sea-level increase due to the actual tsunami began to exceed 1 m after an elapsed time of 25 min. The result suggests a possibility that the forecasting method we used could contribute to the issuing of reliable near-field tsunami warning for M(w) 9 earthquakes.
  • Aditya R. Gusman, Yuichiro Tanioka, Hiroyuki Matsumoto, Sin-Iti Iwasaki
    BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA 99 (4) 2169 - 2179 0037-1106 2009/08 [Refereed][Not invited]
     
    The great outer-rise earthquake (M-w 8.3) occurred near the Sunda trench, Indonesia, on 19 August 1977. The earthquake has been previously studied using seismological data. The earthquake generated a large tsunami that caused severe damage in Sumbawa and Sumba Islands in Indonesia. The tsunami was also observed at tide gauges in Australia. We numerically computed a far-field tsunami, and we compared the observed tsunami waveforms on three tide gauges with the computed waveforms. We also numerically computed the tsunami inundation and compared the observed tsunami run-up of 8 m and tsunami inundation distance of 500 m in Lunyuk on Sumbawa Island with the computed ones. To explain the observed tsunami waveforms, tsunami run-up, and tsunami inundation distance, the slip amount is found to be 3 m on the assumed fault model (with a fault length of 200 km and fault width of 70 km). The rigidity is assumed to range between 6.0 and 6.8 x 10(10) N m(-2), and the range of the total seismic moment is calculated to be between 2.5 and 2.9 x 10(21) N m (M-w 8.2), which is similar to those estimated by the previous seismological studies. Additionally, we calculated the ratio between the observed tsunami run-up and the computed maximum tsunami height along the coastline of Lunyuk. This ratio, called the amplification factor, may possibly be used to roughly estimate the tsunami run-up from a tsunami numerical calculation result on a coarse grid system.
  • Hiroaki Tsushima, Ryota Hino, Hiromi Fujimoto, Yuichiro Tanioka, Fumihiko Imamura
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 114 2169-9313 2009/06 [Refereed][Not invited]
     
    We propose a method for near-field tsunami forecasting from data acquired by cabled offshore ocean bottom tsunami meters (OBTMs) in real time. We first invert tsunami waveforms recorded at OBTMs to estimate the spatial distribution of initial sea-surface displacements in the tsunami source region without making any assumptions about fault geometry and earthquake magnitude. Then, we synthesize the coastal tsunami waveforms from the estimated sea-surface displacement distribution. To improve the reliability of the tsunami forecasting, we use updated OBTM data to repeat the forecast calculation at 1-min intervals. We tested our method by simulating the 1896 Sanriku tsunami earthquake, which caused a devastating tsunami with maximum runup height of 38 m along the Pacific coast of northeastern Japan. Instead of real OBTM records, proxies were used. The simulation demonstrated that our method provided accurate estimations of coastal arrival times and amplitudes of the first peak of the tsunami more than 20 min before the maximum amplitude wave reached the coastal site nearest to the source. We also applied the method to real data of a small tsunami that was caused by a local earthquake and successfully forecasted the tsunami at coastal tide stations. We found that accuracy of our estimated coastal tsunami amplitudes can be affected by the spatial relationship between the tsunami source and the offshore observation stations. Our numerical simulation showed that even more accurate tsunami amplitude forecasts would be achieved by deployment of additional offshore stations separated by a distance comparable to the trench-parallel length of the tsunami source.
  • 谷岡 勇市郎, 西村 裕一, 中村 有吾
    Chikyu monthly 海洋出版 31 (6) 321 - 333 0387-3498 2009/06
  • Hiroyuki Matsumoto, Yuichiro Tanioka, Yuichi Nishimura, Yoshinobu Tsuji, Yuichi Namegaya, Tadashi Nakasu, Sin-Iti Iwasaki
    JOURNAL OF EARTHQUAKE AND TSUNAMI 3 (1) 1 - 15 1793-4311 2009/03 [Refereed][Not invited]
     
    According to the NOAA earthquake database, at least 31 events have been found in the Indian Ocean in terms of tsunami event since 1900, most of which occurred along the Sunda Trench. In this study, we review the history of tide level measurements and their datasets archives in Thailand, Indonesia, India, and Australia. We collected tide gauge paper charts recording historical tsunamis including the 2004 Indian Ocean tsunami in those countries. As a result, systematic collection of historical tsunami records by tide gauges in the Indian Ocean has been difficult, because few tsunamigenic earthquakes occurred in the Indian Ocean during the instrumentally observed period.
  • Kenji Hirata, Kenji Satake, Yuichiro Tanioka, Yohei Hasegawa
    PURE AND APPLIED GEOPHYSICS 166 (1-2) 77 - 96 0033-4553 2009/02 [Refereed][Not invited]
     
    In the southernmost Kuril Trench, the tsunami source regions vary their along-trench extent even among earthquakes occurring within the same segment. Recent studies suggest that the tsunami source of the 1952 Tokachi-oki earthquake (M 8.1) differs from but partially overlaps with that of the 2003 Tokach-oki earthquake (M 8.0). Furthermore, the along-trench extent among the earthquakes seems to differ between deep and shallow portions of the subduction interface. A seismic gap has been recognized along the deep subduction interface between the sources of the 1952 and 1973 earthquakes. We propose that the gap is now larger, including both shallow to deep portions of the interface between the 1973 and 2003 earthquakes. Variability in spatial extent of large subduction earthquakes in both along-trench direction and trench-normal direction makes it difficult to forecast future earthquakes in the southernmost Kuril Trench.
  • Yuichi Namegaya, Yuichiro Tanioka, Kuniaki Abe, Kenji Satake, Kenji Hirata, Masami Okada, Aditya R. Gusman
    PURE AND APPLIED GEOPHYSICS 166 (1-2) 97 - 116 0033-4553 2009/02 [Refereed][Not invited]
     
    Linear and nonlinear responses of ten well-type tide gauge stations on the Japan Sea coast of central Japan were estimated by in situ measurements. We poured water into the well or drained water from the well by using a pump to make an artificial water level difference between the outer sea and the well, then measured the recovery of water level in the well. At three tide gauge stations, Awashima, Iwafune, and Himekawa, the sea-level change of the outer sea is transmitted to the tide well instantaneously. However, at seven tide gauge stations, Nezugaseki, Ryotsu, Ogi, Teradomari, Banjin, Kujiranami, and Naoetsu, the sea-level change of the outer sea is not always transmitted to the tide well instantaneously. At these stations, the recorded tsunami waveforms are not assured to follow the actual tsunami waveforms. Tsunami waveforms from the Niigataken Chuetsu-oki Earthquake in 2007 recorded at these stations were corrected by using the measured tide gauge responses. The corrected amplitudes of the first and second waves were larger than the uncorrected ones, and the corrected peaks are a few minutes earlier than the uncorrected ones at Banjin, Kujiranami, and Ogi. At Banjin, the correction was significant; the corrected amplitudes of the first and second upward motion are +103 cm and +114 cm, respectively, while the uncorrected amplitudes were +96 cm and +88 cm. At other tide gauge stations, the differences between the uncorrected and corrected tsunami waveforms were insignificant.
  • Yuichiro Tanioka
    EARTH PLANETS AND SPACE 60 (2) 123 - 125 1343-8832 2008 [Refereed][Not invited]
     
    The 2007 Noto Hanto earthquake generated a small tsunami that was recorded at several tide gauge stations along the coast of the Japan Sea. The most important feature of this tsunami is that two waveforms recorded at the Wajima and Noto tide gauge stations, which are located 30 km apart, showed very different later phases-the large later phases recorded at Noto were not observed at Wajima. Numerical simulation of the tsunami indicated that the difference was caused by the shallow water bathymetry around the Noto peninsula. The large tsunami that was amplified at a few tens of kilometers off the north coast of the Noto peninsula propagated towards the Noto tide gauge station, but not towards the Wajima station. This study indicates that the propagation of a tsunami caused by a shallow earthquake beneath a coastal area is significantly affected by the local bathymetry. A comparison of the observed and computed tsunami waveforms indicated that the slip amount of the fault was 0.8 m. The seismic moment of the Noto Hanto earthquake was calculated to be 0.94 x 10(19) N m (M-w 6.6).
  • 行谷佑一, 谷岡勇市郎, 阿部邦昭, 佐竹健治, 平田賢治, 岡田正実, Aditya R. Gusman
    津波工学研究報告 東北大学 25 (25) 107 - 122 0916-7099 2008 [Not refereed][Not invited]
  • Hiroaki Tsushima, Ryota Hino, Hiromi Fujimoto, Yuichiro Tanioka
    2007 SYMPOSIUM ON UNDERWATER TECHNOLOGY AND WORKSHOP ON SCIENTIFIC USE OF SUBMARINE CABLES AND RELATED TECHNOLOGIES, VOLS 1 AND 2 612 - + 2007 [Refereed][Not invited]
     
    We developed a new tsunami forecasting method using tsunami data observed at offshore ocean bottom tsunami gauges (OBTGs) in order to improve the reliability of the present tsunami warning system based only on the seismic data. In this method, we invert the OBTGs data for the coseismic sea-floor vertical displacement distribution, and calculate tsunami waveforms at coastal sites by using the inverted displacement field as the tsunami source. The inversion and waveform syntheses require only a minute to be accomplished and the method is applicable to real-time warning system. We performed a numerical test assuming the 1896 Sanriku tsunami earthquake. This result indicates that our method can provide estimations of arrival times and wave heights of tsunamis at coastal sites with five minutes and 60 % accuracy, respectively, five minutes before 8 m height tsunami hits the nearest coastal city. We also applied the method to the small amplitude tsunami caused by a local moderate (M6.8) earthquake and succeeded in explaining the arrival times and amplitudes of the tsunami records obtained at coastal tide stations.
  • Yuichiro Tanioka, Kei Katsumata
    EARTH PLANETS AND SPACE 59 (12) E1 - E3 1343-8832 2007 [Refereed][Not invited]
     
    The 2004 Kushiro-oki earthquake generated a small tsunami that was observed at two tide gauge stations located on the Pacific coast of Hokkaido Province. Analysis of the tsunami waveforms shows that the slip amount of the fault was 2.1 m. The seismic moment was calculated to be 3.1 x 10(19) Nm, which is consistent with the results of previous seismological studies. Tsunami simulation results indicate that a small first wave at Urakawa is caused by large shallow water off Cape Erimo. The tsunami generated from the source area off Kushiro circumvents the shallow area off the cape, propagates through the deep sea, and arrives at Urakawa as a small first wave. Larger tsunamis are propagated through the shallow region slowly and arrive at Urakawa as a later tsunami. These results suggest that a tsunami from a future large Nemuro-oki earthquake will also arrive at the west coast of Hidaka with a small first wave and large later phases.
  • Yuichiro Tanioka, Kenji Satake, Kenji Hirata
    Geophysical Monograph Series 172 1 - 2 2328-8779 2007 [Refereed][Not invited]
     
    Recurrent large earthquakes in the southernmost part of the Kurile-Kamchatka subduction zone were studied. Previous studies have indicated that the 1994 Sanriku-oki earthquake (Mw 7.8) ruptured only the southern part of the rupture area of the 1968 Tokachi-oki earthquake (Mw 8.2), and left the main rupture interface of the 1968 earthquake intact. Also, the 2003 Tokachi-oki earthquake (Mw 8.1) did not rupture the eastern part of the rupture area of the 1952 Tokachioki earthquake (Mw 8.2). The rupture processes of the 1973 and 1894 Nemuro-oki earthquakes were studied through tsunami waveform analyses. The rupture of the 1973 Nemuro-oki earthquake was concentrated on the plate interface off Nemuro, Hokkaido, and the seismic moment was estimated to be 6.5 x 1020 Nm (Mw 7.8). The 1894 Nemuro-oki earthquake ruptured much larger area than that of the 1973 Nemuro-oki earthquake. The fault length of the 1894 earthquake was about 200 km, and the seismic moment was 28.8 x 1020 Nm (Mw 8.3). In this subduction zone, none of three sets of recent recurrent large earthquakes, the 1968 Tokachi and 1994 Sanriku-oki earthquakes, the 1952 and 2003 Tokachi-oki earthquakes, and the 1894 and 1973 Nemuro-oki earthquakes, have the same rupture processes. Variable rupture patterns of large recurrent earthquakes make it difficult to estimate the source processes of future large earthquakes in this subduction zone. These non-regular recurrences also suggest that, in addition to invariant geometric and material heterogeneities, the dynamic stress heterogeneities are seen to be important for understanding large earthquake complexity in this subduction zone.
  • 平田 賢治, 佐竹 健治, 谷岡 勇市郎
    月刊地球 海洋出版 28 (7) 432 - 440 0387-3498 2006/07 [Not refereed][Not invited]
  • Kenji Satake, Kenji Hirata, Shigeru Yamaki, Yuichiro Tanioka
    EARTH PLANETS AND SPACE 58 (5) 535 - 542 1343-8832 2006 [Refereed][Not invited]
     
    Previous studies indicate that the source area of the 2003 Tokachi-oki earthquake (M 8.0) was smaller than the comparable 1952 Tokachi-oki earthquake (M 8.2) source. We reinverted the 1952 tsunami waveforms, by adopting higher-resolution tsunami simulation method, and estimating and correcting for clock errors of tide gauges from comparison of the 1952 and 2003 tsunami waveforms. The estimated slip distribution indicates that the 1952 tsunami source area was indeed larger than the 2003 source. The distributions of measured and computed coastal tsunami heights also support this conclusion.
  • Yuichiro Tanioka, Yudhicara, Tomohiro Kususose, S. Kathiroli, Yuichi Nishimura, Sin-Iti Iwasaki, Kenji Satake
    Earth, Planets and Space 58 (2) 203 - 209 1880-5981 2006 [Refereed][Not invited]
     
    Rupture process of the 2004 Sumatra-Andaman earthquake is estimated using tsunami waveforms observed at tide gauges and the coseismic vertical deformation observed along the coast. The average rupture speed of the 2004 Sumatra-Andaman earthquake is estimated to be 1.7 km/s from tsunami waveform analysis. The rupture extends about 1200 km toward north-northwest along the Andaman trough. The largest slip of 23 m is estimated on the plate interface off the northwest coast in the Aceh province in Sumatra. Another large slip of 21 m is also estimated on the plate interface beneath the north of Simeulue Island in Indonesia. The other large slip of 10-15 m is estimated on the plate interface near Little Andaman and Car Nicobar Inlands. The total seismic moment is calculated to be 7.2 × 1022 Nm (Mw 9.2) which is similar to the other studies using seismic waves (Park et al., 2005 Ammon et al., 2005). Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS) The Seismological Society of Japan The Volcanological Society of Japan The Geodetic Society of Japan The Japanese Society for Planetary Sciences TERRAPUB.
  • Yuichiro Tanioka, Eric L. Geist, Nanang T. Puspito
    Earth, Planets and Space 58 (2) 111  1880-5981 2006 [Refereed][Not invited]
  • Hirata, K, K. Satake, Y. Tanioka, T. Kuragano, Y. Hasegawa, Y. Hayashi, N. Hamada
    Earth Planets and Space 58 (2) 195 - 201 1343-8832 2006 [Not refereed][Not invited]
  • Field Survey of the 2003 Tokachi-Oki Earthquake Tsunami and Simulation at the Ootsu Harbor Located at the Pacific Coast of Hokkaido, Japan
    Yuichiro Tanioka, Yuichi Nishimura, Kazuomi Hirakawa, Fumihiko Imamura, Ikuo Abe, Yoshi Abe, Kazuya Shindou, Hideo Matsutomi, Tomoyuki Takahashi, Kentaro Imai, Koji Fujima, Kenji Harada, Yuichi Namegaya, Yohei Hasegawa, Yutaka Hayashi, Akifumi Yoshikawa, Toru Shiga, Akiyasu Kamikawa, Masaki Kobayashi, Seiichi Masaka, Takanobu Kamataki, Futoshi Nanayama, Kenji Satake, Yoshiaki Kawata, Yoshinobu Fukasawa, Shunichi Koshimura, Yasunori Hada, Yusuke Azumai, Kenji Hirata
    Tsunamis Case Studies and Recent Developments, Advances in Natural and Technological Hazards Research Vol.23, pp.135-156 2005 [Not refereed][Not invited]
  • 平田 賢治, 谷岡 勇市郎, 佐竹 健治
    号外地球 海洋出版 (49) 162 - 167 0916-9733 2005 [Not refereed][Not invited]
  • 佐竹 健治, 平田 賢治, 谷岡 勇市郎
    号外地球 海洋出版 (49) 56 - 64 0916-9733 2005 [Not refereed][Not invited]
  • Kenji Hirata, Yuichiro Tanioka, Kenji Satake, Shigeru Yamaki, Eric L. Geist
    Earth, Planets and Space 56 (3) 367 - 372 1880-5981 2004 [Refereed][Not invited]
     
    We estimate the tsunami source area of the 2003 Tokachi-oki earthquake (Mw 8.0) from observed tsunami travel times at 17 Japanese tide gauge stations. The estimated tsunami source area (∼1.4 × 104 km2) coincides with the western-half of the ocean-bottom deformation area (∼2.52 × 104 km2) of the 1952 Tokachi-oki earthquake (Mw 8.1), previously inferred from tsunami waveform inversion. This suggests that the 2003 event ruptured only the western-half of the 1952 rupture extent. Geographical distribution of the maximum tsunami heights in 2003 differs significantly from that of the 1952 tsunami, supporting this hypothesis. Analysis of first-peak tsunami travel times indicates that a major uplift of the ocean-bottom occurred approximately 30 km to the NNW of the mainshock epicenter, just above a major asperity inferred from seismic waveform inversion. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS) The Seismological Society of Japan The Volcanological Society of Japan The Geodetic Society of Japan The Japanese Society for Planetary Sciences.
  • Y Tanioka, K Hirata, R Hino, T Kanazawa
    EARTH PLANETS AND SPACE 56 (3) 373 - 376 1343-8832 2004 [Refereed][Not invited]
     
    The slip distribution of the 2003 Tokachi-oki earthquake is estimated from the 11 tsunami waveforms recorded at 9 tide gauges in the southern Hokkaido and eastern Tohoku coasts and two ocean bottom tsunami-meters (pressure gauges) off Kamaishi, Tohoku. The largest slip of 4.3 m is estimated on the subfault located off Hiroo. A large slip of 2.1 m is also estimated on the subfault located near Kushiro. The total seismic moment of the 2003 Tokachi-oki earthquake is 1.0 x 10(21) Nm. The slip distribution estimated from the tsunami waveform inversion is similar to the slip distribution deduced by Yamanaka and Kikuchi (2003) from the inversion of the teleseismic body waves. The rupture area of the 2003 Tokachi-oki earthquake is similar to the western part of the rupture area of the 1952 Tokachi-oki earthquake estimated by Hirata et al. (2003).
  • Tanioka, Y, co-authors, h, Y. Hayashi
    Earth, Planets and Space 56 (3) 359 - 365 1343-8832 2004 [Refereed][Not invited]
  • Kenji Satake, Yuichiro Tanioka
    Pure and Applied Geophysics 160 (10-11) 2087 - 2118 0033-4553 2003/10 [Refereed][Not invited]
     
    The unusual tsunami generated by the July 17, 1998 Papua New Guinea earthquake was investigated on the basis of various geophysical observations, including seismological data, tsunami waveform records, and on-land and submarine surveys. The tsunami source models were constructed for seismological high-angle and low-angle faults, splay fault, and submarine slumps. Far-field and near-field tsunamis computed from these models were compared with the recorded waveforms in and around Japan and the measured heights along the coast around Sissano Lagoon, respectively. In order to reproduce the far-field tsunami waveforms, small sources such as splay fault or submarine slump alone were not enough, and a seismological fault model was required. Relocated aftershock distribution and observed coastal subsidence were preferable for the low-angle fault, but the low-angle fault alone could not reproduce the large near-field tsunamis. The low-angle fault with additional source, possibly a submarine slump, is the most likely source of the 1998 tsunami, although other possibilities cannot be excluded. Computations from different source models showed that the far-field tsunami amplitudes are proportional to the displaced water volume at the source, and the comparison with the observed tsunami amplitudes indicated that the displaced water volume at the 1998 tsunami source was ∼0.6 km3. The near-filed tsunami heights, on the other hand, are determined by the potential energy of displaced water, and the comparison with the observed heights showed that the potential energy was ∼2 × 1012 J.
  • 谷岡 勇市郎, 佐竹 健治
    月刊地球 海洋出版 25 (5) 347 - 354 0387-3498 2003/05 [Not refereed][Not invited]
  • K Hirata, H Takahashi, E Geist, K Satake, Y Tanioka, H Sugioka, H Mikada
    EARTH AND PLANETARY SCIENCE LETTERS 208 (3-4) 305 - 318 0012-821X 2003/03 [Refereed][Not invited]
     
    Micro-tsunami waves with a maximum amplitude of 4-6 turn were detected with the ocean-bottom pressure gauges on a cabled deep seafloor observatory south of Hokkaido, Japan, following the January 28, 2000 earthquake (M-w 6.8) in the southern Kuril subduction zone. We model the observed micro-tsunami and estimate the focal depth and other source parameters such as fault length and amount of slip using grid searching with the least-squares method. The source depth and. stress drop for the January 2000 earthquake are estimated to be 50 km and 7 MPa, respectively, with possible ranges of 45-55 km and 4-13 MPa.. Focal depth of typical inter-plate earthquakes in this region ranges from 10 to 20 km and stress drop of inter-plate earthquakes generally is around 3 MPa. The source depth and stress drop estimates suggest that the earthquake was an intra-slab event in the subducting Pacific plate, rather than an inter-plate event. In addition, for a prescribed fault width of 30 kin, the fault length is estimated to be 15 kin, with possible ranges of 10-20 km, which is the same as the previously determined aftershock distribution. The corresponding estimate for seismic moment is 2.7 X 10(19) Nm with possible ranges of 23 X 10(19)-3.2 X 10(19) Nm. Standard tide gauges along the nearby coast did not record any tsunami signal. High-precision ocean-bottom pressure measurements offshore thus make it possible to determine fault parameters of moderate-sized earthquakes in subduction zones using open-ocean tsunami waveforms. Published by Elsevier Science B.V.
  • Toshitaka Baba, Yuichiro Tanioka, Phil R Cummins, Koichi Uhira
    Physics of the Earth and Planetary Interiors Vol.132 (No.1-3) 59 - 73 0031-9201 2002/09 [Refereed][Not invited]
  • Yuichiro Tanioka, Tetsuzo Seno
    Geophysical Research Letters 28 (17) 3389 - 3392 0094-8276 2001/09/01 [Refereed][Not invited]
     
    The 1896 Sanriku earthquake was one of the most devastating tsunami earthquakes, which generated an anomalously larger tsunami than expected from its seismic waves. Previous studies indicate that the earthquake occurred beneath the accretionary wedge near the trench axis. It was pointed out recently that sediments near a toe of an inner trench slope with a large horizontal movement due to the earthquake might have caused an additional uplift. In this paper, the effect of the additional uplift to tsunami generation of the 1896 Sanriku tsunami earthquake is quantified. We estimate the slip of the earthquake by numerically computing tsunamis and comparing their waveforms with those recorded at three tide gauges. The estimated slip for the model without the additional uplift is 10.4 m, and those with the additional uplift are 5.9-6.7 m. This indicates that the additional uplift of the sediments near the trench has a large effect on the tsunami generation.
  • Yuichiro Tanioka, Kenji Satake
    Earth, Planets and Space 53 (4) 235 - 241 1880-5981 2001 [Refereed][Not invited]
     
    Coseismic slip distribution on the fault plane of the 1946 Nankai earthquake (Mw 8.3) was estimated from inversion of tsunami waveforms. The following three improvements from the previous study (Satake, 1993) were made. (1) Larger number of smaller subfaults is used (2) the subfaults fit better to the slab geometry and (3) more detailed bathymetry data are used. The inversion result shows that the agreement between observed and synthetic waveforms is greatly improved from the previous study. In the western half of the source region off Shikoku, a large slip of about 6 m occurred near the down-dip end of the locked zone. The slip on the up-dip or shallow part was very small, indicating a weak seismic coupling in that region. In the eastern half of the source region off Kii peninsula, a large slip of about 3 m extended over the entire locked zone. Large slips on the splay faults in the upper plate estimated from geodetic data (Sagiya and Thatcher, 1999) were not required to explain the tsunami waveforms, suggesting that the large slips were aseismic. Two slip distributions on the down-dip end of the plate interface, one from geodetic data and the other from tsunami waveforms, agree well except for slip beneath Cape Muroto in Shikoku. This suggests that aseismic slip also occurred on the plate interface beneath Cape Muroto. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS) The Seismological Society of Japan The Volcanological Society of Japan The Geodetic Society of Japan The Japanese Society for Planetary Sciences.
  • Yuichiro Tanioka
    Papers in Meteorology and Geophysics 51 (1) 17 - 25 0031-126X 2000 [Refereed][Not invited]
     
    The dispersion effect is not negligible in the numerical simulation of far-field tsunamis propagating through deep oceans. Imamura et al. (1990) introduced a technique in which the discretization error in the finite difference equation of the linear long wave equation was used to approximate the physical dispersion term. The technique is widely accepted to compute trans-Pacific tsunamis caused by great earthquakes (Mw > 8). However, the technique has never been applied to compute tsunamis caused by smaller earthquakes (Mw < 7) because the approximation may break down. In order to compute the tsunami caused by the 1998 Papua New Guinea earthquake (Mw 7.1), we numerically solve the linear Boussinesq equation, which includes the physical dispersion term, using an implicit scheme. For comparison, we also compute the tsunami using Imamura's technique. The comparison of the computed waveforms at the ocean bottom pressure gauge off Boso (BS3-OBP) from the two numerical simulations indicates that the linear Boussinesq equation should be used to simulate the tsunami waveform more accurately, especially the later phase of tsunami waveforms. We also found that the observed tsunami that was originally generated by the 1998 Papua New Guinea earthquake and recorded at BS3-OBP was a ridge wave. The ridge wave was enhanced by the shallow water region around the Izu-Bonin Islands.
  • Yuichiro Tanioka
    Geophysical Research Letters 26 (22) 3393 - 3396 0094-8276 1999/11/15 [Refereed][Not invited]
     
    The tsunami generated by the 1998 Papua New Guinea earthquake was observed at several tide gauges and ocean bottom pressure gauges in Japan. The fault model of the 1998 Papua New Guinea earthquake was estimated using those tsunami waveforms observed in Japan and coseismic subsidence observed along the coast of Papua New Guinea near the source region. The numerical simulation of the tsunami using the linear Boussinesq equation was carried out. The tsunami waveforms in Japan are explained by the fault model which is consistent with the Harvard CMT solution including the seismic moment of 3.7 X 1019 Nm. The additional tsunami source, such as a sediment slump, is not needed to explain the observed tsunami in Japan. The mechanism of the earthquake was likely to be a steeply dipping reverse fault. The 1998 Papua New Guinea earthquake was likely to occur within a small accretionary prism near the New Guinea trench.
  • 谷岡 勇市郎, 佐竹 健治
    号外地球 海洋出版 (24) 21 - 25 0916-9733 1999/03 [Not refereed][Not invited]
  • Yuichiro Tanioka, Frank I. Gonzalez
    Geophysical Research Letters 25 (12) 2245 - 2248 0094-8276 1998/06/15 [Refereed][Not invited]
     
    The epicenter of the Aleutian earthquake of June 10, 1996, is located in the Delarof segment where a large subduction earthquake is expected. However, the aftershock area of the earthquake is not only in the Delarof segment but also in the Andreanof segment where the 1986 Andreanof earthquake occurred previously. We estimate the fault parameters of the 1996 earthquake by numerically computing the tsunami and comparing the waveforms with that recorded at Adak. The fault width is 30 km or less, and the average slip is about 4 m. The observed far-field tsunamis around the Pacific are also explained by the synthetic tsunami computed using the above fault parameters. The results indicate that the 1996 earthquake ruptured parts of both the Delarof and Andreanof segments. However, the 1996 earthquake did not rupture the region of the largest moment release by the 1986 earthquake. Copyright 1998 by the American Geophysical Union.
  • 佐竹 健治, 谷岡 勇市郎
    地學雜誌 公益社団法人 東京地学協会 106 (4) 546 - 556 0022-135X 1997/08/25 [Not refereed][Not invited]
     
    We estimated the fault parameters of the 1995 Amami-Oshima-Kinkai Earthquake, which occurred along the Ryukyu trench with a normal fault mechanism. The earthquake generated larger tsunamis than expected from its magnitude (<I>M</I><SUB>JMA</SUB> 6.7), about 3 m on nearby Kikai-jima Island. Among six fault models we considered, the low angle fault dipping to the east (model LA) best explains the observed data such as the aftershock distribution and the horizontal coseismic movement of Amami-Oshima Island inferred from GPS measurements. The fault is 60 km long, 30 km wide, 10-20km deep and the average slip on the fault is 1 m. Tsunami numerical computations indicate that the tsunami amplitudes, particularly at far-field, are insensitive to the fault parameters, suggesting that the large tsunami was not due to unusual source process. Numerical computations also show that the bathymetry between the source and Kikai-jima Island is responsible to the large tsunamis observed on the island.
  • Yuichiro Tanioka, Larry Ruff, Kenji Satake
    Island Arc 6 (3) 261 - 266 1038-4871 1997 [Refereed][Not invited]
     
    The lateral (along trench axis) variation in the mode of large earthquake occurrence near the northern Japan Trench is explained by the variation in surface roughness of the subducting plate. The surface roughness of the ocean bottom near the trench is well correlated with the large-earthquake occurrence. The region where the ocean bottom is smooth is correlated with 'typical' large underthrust earthquakes (e.g. the 1968 Tokachi-oki event) in the deeper part of the seismogenic plate interface, and there are no earthquakes in the shallow part (aseismic zone). The region where the ocean bottom is rough (well-developed horst and graben structure) is correlated with large normal faulting earthquakes (e.g. the 1933 Sanriku event) in the outer-rise region, and large tsunami earthquakes (e.g. the 1896 Sanriku event) in the shallow region of the plate interface zone. In the smooth surface region, the coherent metamorphosed sediments form a homogeneous, large and strong contact zone between the plates. The rupture of this large strong contact causes great underthrust earthquakes. In the rough surface region, large outer-rise earthquakes enhance the well-developed horst and grabens. As these structure are subducted with sediments in the graben part, the horsts create enough contact with the overriding block to cause an earthquake in the shallow part of the interface zone, and this earthquake is likely to be a tsunami earthquake. When the horst and graben structure is further subducted, many small strong contacts between the plates are formed, and they can cause only small underthrust earthquakes.
  • 谷岡 勇市郎, 佐竹 健治
    科学 岩波書店 66 (8) 574 - 581 0022-7625 1996/08 [Not refereed][Not invited]
  • Yuichiro Tanioka, Kenji Satake
    Geophysical Research Letters 23 (13) 1549 - 1552 0094-8276 1996 [Refereed][Not invited]
     
    The June 15, 1896 Sanriku earthquake generated devastating tsunamis with the maximum run-up of 25 m and caused the worst tsunami disaster in the history of Japan, despite its moderate surface wave magnitude (MS=7.2) and weak seismic intensity. This is a typical tsunami earthquake, which generates anomalously larger tsunamis than expected from its seismic waves. Previously proposed mechanisms of tsunami earthquakes include submarine slumping and slow rupture in the accretionary wedge or in the subducted sediments. In this paper, we estimate the fault parameters of the 1896 tsunami earthquake by numerically computing the tsunami and comparing the waveforms with those recorded at three tide gauge stations in Japan. The result indicates that the tsunami source is very close to the Japan trench and the fault strike is parallel to the trench axis. The fault width is about 50 km, suggesting that the tsunami earthquake is a slow rupture in the subducted sediments beneath the accretionary wedge. Copyright 1996 by the American Geophysical Union.
  • Yuichiro Tanioka, Larry Ruff, Kenji Satake
    Geophysical Research Letters 23 (12) 1465 - 1468 0094-8276 1996 [Refereed][Not invited]
     
    Fault geometry, depth, and slip distribution of the Sanriku-oki earthquake of December 28, 1994 (Ms 7.5) are estimated from seismic waveforms, geodetic measurements, and tsunami waveforms, and compared with those of the 1968 Tokachi-oki earthquake (Mw 8.2), the most recent large earthquake in the epicentral region. Seismic wave inversions indicate a shallowly dipping thrust type mechanism and the focal depth of 22-28 km, representing an underthrust event at the subduction interface. The source time function has an initial stage of 20 s followed by a main pulse of 30 s duration, a shape similar to that of the 1968 Tokachi-oki earthquake. Joint inversion of geodetic and tsunami data shows that the region of the largest slip, 1.7 m, corresponds to a region of relatively small slip for the 1968 Tokachi-oki earthquake. Furthermore, the joint inversion shows that the region of the largest asperity of the 1968 earthquake had essentially zero slip during the 1994 Sanriku-oki earthquake. These results indicate that the dominant asperities ruptured by the 1994 Sanriku and 1968 Tokachi-oki earthquakes are different. The result of the joint inversion also shows that the aseismic zone near the Japan trench was not ruptured by the 1994 earthquake. Copyright 1996 by the American Geophysical Union.
  • Yuichiro Tanioka, Kenji Satake
    Geophysical Research Letters 23 (8) 861 - 864 0094-8276 1996 [Refereed][Not invited]
     
    Tsunami generation by an earthquake is generally modeled by water surface displacement identical to the vertical deformation of ocean bottom due to faulting. The effect of horizontal deformation is usually neglected. However, when the tsunami source is on a steep slope and the horizontal displacement is large relative to the vertical displacement, the effect becomes significant. We show this for two recent earthquakes which generated much larger tsunamis than expected from seismic waves. In the case of the 1994 June 2 Java, Indonesia, earthquake, the focal mechanism was a very shallow dipping thrust and the source was near a very steep trench slope. In the case of the 1994 Nov. 14 Mindoro, Philippines, earthquake, strike-slip faulting extended from ocean to land perpendicular to the coast line. In both cases, we found that the horizontal motion of slope had an important contribution to the tsunami generation. Copyright 1996 by the American Geophysical Union.

MISC

  • TANIOKA Yuichiro, GUSMAN Aditya R  Zisin (Journal of the Seismological Society of Japan. 2nd ser.)  64-  (4)  265  -270  2012/06/25  [Refereed][Not invited]
     
    Review of the previous tsunami analyses for the 2011 Tohoku-oki earthquake indicates that the large slip of more than 40m was estimated on the plate interface near the Japan Trench. The plate interface near the Japan Trench was previously ruptured by the tsunami earthquakes such as 1896 or 1611 Sanriku tsunami earthquakes. Along the subduction zone off Sumatra, the 2004 great Sumatra earthquake ruptured the plate interface near the trench with a large slip amount of 29m. There were also tsunami earthquakes such as the 1907 Sumatra earthquake or 2010 Mentawai earthquake which ruptured the plate interface close to the trench. These evidences suggest that occurrence of the large earthquakes which rupture the plate interface near trench such as tsunami earthquakes is more common than that we thought previously. Variability of the great earthquakes along the plate interface makes us difficult to evaluate future great interplate earthquakes along subduction zones.
  • 谷岡 勇市郎  日本地震学会ニュースレター : News letter  23-  (3)  18  -20  2011/09/10  [Not refereed][Not invited]
  • TANIOKA Yuichiro  Zisin : Journal of the Seismological Society of Japan  61-  (0)  S489  -S496  2009/07/31  [Not refereed][Not invited]
     
    Studies in Japan on earthquake source processes and tsunami generation using tsunami data during recent 15 yeas are reviewed. The new tsunami observation systems including ocean bottom tsunami meters, GPS tsunami meters, and ultrasonic wave meters, have been developed recently. The methods using the tsunami waveform data observed by those advanced systems have also been developed and the detail source processes of the recent large earthquakes are studied using those methods and data. Studies on 2004 Sumatra-Andaman great earthquake, which caused the worst tsunami disaster and affected the countries around the Indian Ocean, are reviewed. Next, studies on source models of historical large earthquakes using tsunami data are reviewed. Researches on the mechanism of tsunami earthquakes are also reviewed. Finally, tsunami studies on submarine landslides triggered by earthquakes are reviewed.
  • IOKI Kei, TANIOKA Yuichiro  Zisin : Journal of the Seismological Society of Japan  61-  (3)  145  -148  2009/03/30  [Not refereed][Not invited]
  • HIRATA Kenji, SATAKE Kenji, YAMAKI Shigeru, TANIOKA Yuichiro, YAMANAKA Yoshiko, NISHIMURA Takuya  Zisin : Journal of the Seismological Society of Japan  60-  (1)  21  -41  2007/08/25  [Not refereed][Not invited]
  • TANIOKA Yuichiro, HINO Ryota, HASEGAWA Yohei  Zisin : Journal of the Seismological Society of Japan  59-  (4)  385  -387  2007/03/25  [Not refereed][Not invited]
  • 2004年スマトラ島沖地震津波による最大被災地Banda Aceh市とその周辺海岸の津波の浸水高さ
    都司嘉宣, 谷岡勇市郎, 松富英夫, 西村裕一, 村上嘉謙, 榊山 勉, A.Moore, G.Gelfbaum, S.Nugroho, B.Waluyo, I.Sukanta, R.Triyono  月刊地球  号外56-  154  -166  2006  [Not refereed][Not invited]
  • HAYASHI Yutaka, HIRATA Kenji, HAMADA Nobuo, SATAKE Kenji, TANIOKA Yuichiro, KURAGANO Tsurane, SAKURAI Toshiyuki, TAKAYAMA Hiromi, HASEGAWA Yohei  Technical report of IEICE. SANE  105-  (158)  91  -96  2005/06/22  [Not refereed][Not invited]
     
    Two phenomena associated with huge earthquakes have been observed after the 2004 Sumatra-Andaman earthquake for the first time by using satellite altimetry. One is the height distribution of the propagating tsunami in the ocean. The other is the seismic geoid change. The following is an outline of our tentative research results reported in this paper: (1) estimation by inverse analysis with numerical tsunami computation and the detected tsunami propagating in the Indian Ocean and (2) estimation of fault location from seismic geoid change. We also draw attention to the fact that satellite ob...
  • 松富英夫, 榊山 勉, S.Nugroho, 都司嘉宣, 谷岡勇市郎, 西村裕一, 鎌滝孝信, 村上嘉謙, 松山昌史, 栗塚一範  海岸工学論文集  52-  1366  -1370  2005  [Not refereed][Not invited]
  • Tsunami Height Survey of the 2004 off the Kii Peninsula Earthquakes
    Nobuaki Koike, Shunichi Koshimura, Tomoyuki Takahashi, Yoshiaki Kawata, Fumihiko Imamura, Kenji Harada, Koji Fujima, Yoshinori Shigihara, YuichiroTanioka, Yuichi Nishimura, Teruyuki Kato, Yukihiro Terada, Shingo Suzuki, Yoshihiro Okumura  Annual Journal of Coastal Engineering, JSCE  第52巻, pp.1336-1340-  2005  [Not refereed][Not invited]
  • TANIOKA Yuichiro, HIRATA Kenji, HINO Ryota, KANAZAWA Toshihiko  Zisin : Journal of the Seismological Society of Japan  57-  (2)  75  -81  2004/12/27  [Not refereed][Not invited]
  • NISHIMURA Yuichi, TANIOKA Yuichiro, HIRAKAWA Kazuomi  Zisin : Journal of the Seismological Society of Japan  57-  (2)  135  -138  2004/12/27  [Not refereed][Not invited]
  • 谷岡 勇市郎, 西村 裕一, 平川 一臣, 今村 文彦, 阿部 郁男, 安部 祥, 進藤 一弥, 松冨英夫, 高橋智幸, 今井 健太郎, 大沼 康太郎, 神 昭平, 村上 哲朗, 都司 嘉宣, 行谷 佑一, 藤間 功司, 真坂 誠一, 長谷川 洋平, 林 豊, 吉川 章文, 上川 明保, 志賀 透, 小林 政樹, 小田 勝也, 富田 孝史, 柿沼 太郎, 佐竹 健治, 七山 太, 鎌滝 孝信, 平田 賢治, 河田 恵昭, 深澤 良信, 越村 俊一, 秦 康範, 東井 裕介  津波工学研究報告  21-  (0)  [調査報告]1  -200  2004/03/30  [Not refereed][Not invited]
  • TANIOKA Yuichiro  Zisin : Journal of the Seismological Society of Japan  56-  (4)  405  -411  2004/03/25  [Not refereed][Not invited]
  • 津波波形インバージョンによる1944年東南海地震のすべり量分布再解析
    谷岡 勇市郎, Toshitaka Baba  月間地球  (No.26)  754  -758  2004  [Not refereed][Not invited]
  • Field Survey of the 2003 Tokachi-oki Earthquake Tsunami
    Tomoyuki Takahashi, Fumihiko Imamura, YuichiroTanioka, Yuichi Nishimura, Hideo Matsutomi, Yohei Hasegawa, Masaki Kobayashi, Akiyasu Kamikawa, Futoshi Nanayama, Seiichi Masaka, Koji Fujima, Kenji Harada, Shunichi Koshimura, Takashi Tomita  Annual Journal of Coastal Engineering, JSCE  第51巻, pp.1356-1360-  2004  [Not refereed][Not invited]
  • Toshitaka Baba, 谷岡 勇市郎  Chikyu Monthly  Vol.23-  (No.10)  697  -702  2001/10  [Not refereed][Not invited]

Educational Activities

Teaching Experience

  • Prognosis of Earthquakes and Volcanic Eruptions
    開講年度 : 2020
    課程区分 : 修士課程
    開講学部 : 理学院
    キーワード : 地震 津波  火山噴火  防災
  • Exercises in Field Geophysics
    開講年度 : 2020
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 地震観測データ解析、津波観測データ解析、多項目測定、地下構造探査データ解析
  • Freshman Seminar
    開講年度 : 2020
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 巨大地震、巨大津波

Campus Position History

  • 2016年4月1日 
    2018年3月31日 
    理学研究院附属地震火山研究観測センター長

Position History

  • 2016年4月1日 
    2018年3月31日 
    理学研究院附属地震火山研究観測センター長


Copyright © MEDIA FUSION Co.,Ltd. All rights reserved.