Researcher Profile and Settings

Master

Affiliation (Master)

• Faculty of Science　Institute of Seismology and Volcanology

Affiliation (Master)

• Faculty of Science　Institute of Seismology and Volcanology

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Profile and Settings

Degree

• Ph D.（2011/03 Tohoku University）

Profile and Settings

• Name (Japanese)

  Ohzono

• Name (Kana)

  Mako

• Name

  201301071784135140

Achievement

Research Interests

• crustal deformation   Geodecy   Seismology   Volcanology   

Research Areas

• Natural sciences / Solid earth science

Research Experience

• 2024/04 - Today Hokkaido University Institute of Seismology and Volcanology, Faculty of Science Professor
• 2019/10 - 2024/03 Hokkaido University Institute of Seismology and Volcanology, Faculty of Science Associate Professor
• 2020/04 - 2022/03 The University of Tokyo Earthquake Research Institute Coordination Center for Prediction Research of Earthquakes and Volcanic Eruptions
• 2016/04 - 2019/09 Hokkaido University Institute of Seismology and Volcanology, Faculty of Science Lecturer
• 2013/04 - 2016/03 Yamagata University Faculty of Science Lecturer
• 2011/04 - 2013/03 Hokkaido University Graduate School of Science Post-doc.

Education

• 2007/10 - 2011/03  Tohoku University
• 2004/04 - 2007/03  Nagoya University
• 2000/04 - 2004/03  Kochi University

Committee Memberships

• 2020/08 - Today   JpGU   Solid Earth Sciences Section borad

Awards

• 2015/03 山形大学 平成26年度山形大学理学部ベストティーチャー賞
   

  受賞者: 大園 真子
• 2014/04 Seismological Society of Japan 2013 Paper award
   

  受賞者: Mako Ohzono
• 2011/03 東北大学青葉理学振興会 黒田チカ賞
   

  受賞者: 大園 真子
• 2009/10 日本測地学会 学生による優秀発表賞
   

  受賞者: 大園 真子

Published Papers

• Geodetic plate coupling and seismic potential on the main Himalayan thrust in Nepal

  Takao Tabei, Mako Ohzono, Bishow R. Silwal, Rajendra P. Bhandari, Lok B. Adhikari, Janak B. Chand, Thakur P. Kandel

  Earth Planets Space 76 68  2024/05/08 [Refereed]
  
• Stress field in northeastern Japan and its relationship with faults of recent earthquakes

  Ayaka Tagami, Miu Matsuno, Tomomi Okada, Shin’ichi Sakai, Mako Ohzono, Kei Katsumata, Masahiro Kosuga, Yoshiko Yamanaka, Hiroshi Katao, Takeshi Matsushima, Hiroshi Yakiwara, Satoshi Hirahara, Toshio Kono, Shu’ichiro Hori, Toru Matsuzawa, Shuutoku Kimura, Takashi Nakayama

  Earth, Planets and Space 76 (1) 2024/03/07 [Refereed]
   

  Abstract Inversion tectonics, in which old normal faults act as reverse faults in current stress fields, are frequently observed in northeastern Japan (Tohoku District); however, the conditions that control these fault activities remain unclear. To improve the identification of faults that are more favorable to slip under current stress conditions, the regional fault mechanisms in the Tohoku District must be better understood. The stress field in the Tohoku District and the likelihood of fault activities were thus estimated using slip tendency (ST) analysis. The results show that in the eastern margin of the Japan Sea (EMJS), the reverse fault type is dominant in the stress field. The maximum horizontal direction changes clockwise from E–W to NW–SE from the northern to the southern regions and counterclockwise from NW–SE to E–W from the Japan Sea to the inland area. In the Tohoku inland area, the estimated direction of the maximum horizontal axis changed after the 2011 Tohoku-Oki earthquake, from E–W to WNW–ESE. ST values were calculated for seven events in the EMJS area. To avoid the influence of the Tohoku-Oki earthquake, only stress field data prior to the 2011 Tohoku-Oki earthquake were used to determine ST values for four of the events in the Tohoku inland area. The results showed eastward-dipping fault planes with low dip angles (approximately 30°–45°) and large ST values (approximately > 0.7). The large ST values indicate that the stress field fault is favorable to slip and the results were consistent with the actual fault plane in the EMJS area. However, in the Tohoku inland area and the southern part of fault model of the 1993 Hokkaido Nansei-Oki earthquake, fault planes with large ST values were found to be inconsistent with the slipped fault plane, thus indicating that slipping was unfavorable. The regional differences are consistent with the volcano distribution and thus, the fluid supply from volcanic activity may have helped the fault slip under difficult stress conditions. Graphical Abstract
• Solidified magma reservoir derived from active source seismic experiments in the Aira caldera, southern Kyushu, Japan

  Hiroki Miyamachi, Hiroshi Yakiwara, Reiji Kobayashi, Shuichiro Hirano, Takeshi Kubo, Masakazu Souda, Kenyu Sakao, Naohiro Unno, Takeshi Matsushima, Kazunari Uchida, Rintaro Miyamachi, Kenshin Isoda, Yoshiko Teguri, Yoshinosuke Kamiya, Agnis Triahadini, Hiroshi Shimizu, Hiroshi Katao, Takuo Shibutani, Takeshi Tameguri, Yusuke Yamashita, Tsutomu Miura, Jun Nakagawa, Itaru Yoneda, Shinya Kato, Kosei Takishita, Kazuho Nakai, Yuta Maeda, Toshiki Watanabe, Shinichiro Horikawa, Kenjiro Matsushiro, Takashi Okuda, Shuhei Tsuji, Naoki Sogawa, Daima Hasegawa, Kazuo Nakahigashi, Eiji Kurashimo, Tomoaki Yamada, Hideji Abe, Miwako Ando, Shinichi Tanaka, Satoshi Ikezawa, Takaya Iwasaki, Masanao Shinohara, Toshinori Sato, Mare Yamamoto, Ryosuke Azuma, Satoshi Hirahara, Takashi Nakayama, Syuichi Suzuki, Shuhei Otomo, Ryota Hino, Tomoki Tsutsui, Yusuke Inoue, Ryuichi Takei, Yuya Tada, Hiroaki Takahashi, Yoshio Murai, Hiroshi Aoyama, Mako Ohzono, Takahiro Shiina, Masamitsu Takada, Masayoshi Ichiyanagi, Teruhiro Yamaguchi, Natsuki Ono, Kazuma Saito, Chihiro Ito, Yuuki Susukida, Tatsuya Nakagaki, Yasuhisa Tanaka, Yasuhiko Akinaga

  Earth, Planets and Space 75 (1) 2023/10/18 [Refereed]
   

  Abstract The Aira caldera, located in southern Kyushu, Japan, originally formed 100 ka, and its current shape reflects the more recent 30 ka caldera-forming eruptions (hereafter, called the AT eruptions). This study aimed to delineate the detailed two-dimensional (2D) seismic velocity structure of the Aira caldera down to approximately 15 km, by means of the travel-time tomography analysis of the seismic profile across the caldera acquired in 2017 and 2018. A substantial structural difference in thickness in the subsurface low-velocity areas in the Aira caldera between the eastern and western sides, suggest that the Aira caldera comprises at least two calderas, identified as the AT and Wakamiko calderas. The most interesting feature of the caldera structure is the existence of a substantial high-velocity zone (HVZ) with a velocity of more than 6.8 km/s at depths of about 6–11 km beneath the central area of the AT caldera. Because no high ratio of P- to S-wave velocity zones in the depth range were detected from the previous three-dimensional velocity model beneath the AT caldera region, we infer that the HVZ is not an active magma reservoir but comprises a solidified and cool remnant. In addition, a poorly resolved low-velocity zone around 15 km in depth suggests the existence of a deep active magma reservoir. By superimposing the distribution of the known pressure sources derived from the observed ground inflation and the volcanic earthquake distribution onto the 2D velocity model, the magma transportation path in the crust was imaged. This image suggested that the HVZ plays an important role in magma transportation in the upper crust. Moreover, we estimated that the AT magma reservoir in the 30 ka Aira caldera-forming eruptions has the total volume of 490 km³ DRE and is distributed in a depth range of 4–11 km. Graphical Abstract
• Conceptual model of supercritical geothermal system in Shiribeshi Region, Hokkaido, Japan

  Daisuke Oka, Makoto Tamura, Toru Mogi, Mitsuhiro Nakagawa, Hiroaki Takahashi, Mako Ohzono, Masayoshi Ichiyanagi

  Geothermics 108 102617 - 102617 0375-6505 2023/02 [Refereed]
  
• Application of machine learning methods for detection of covolcanic ionospheric disturbances by GNSS observations data

  A.S. Ten, N.V. Shestakov, A.А. Sorokin, N.N. Titkov, M. Ohzono, H. Takahashi

  Modern problems of remote sensing from space 20 (1) 37 - 54 2070-7401 2023 [Refereed]
  
• Potential for crustal deformation monitoring using a dense cell phone carrier Global Navigation Satellite System network

  Yusaku Ohta, Mako Ohzono

  Earth, Planets and Space 74 (1) 2022/02/09 [Refereed]
   

  Abstract Monitoring of crustal deformation provides essential information for seismology and volcanology. For such earth science fields and other purposes, various Global Navigation Satellite System (GNSS) networks have been constructed at the national and regional levels. In Japan, the continuous nationwide GNSS network, the GNSS Earth Observation Network System (GEONET), is operated by the Geospatial Information Authority of Japan. Although GEONET has made a substantial contribution to earth science research, the large spacing of GEONET sites makes it difficult to accurately understand crustal deformation phenomena in some cases. However, cell phone carriers in Japan have constructed independent GNSS networks to improve their positioning services in recent years. In this study, we examine the performance of a GNSS network operated by SoftBank Corp. for crustal deformation monitoring. The network has more than 3300 sites throughout Japan, which is approximately 2.5 times the number of the GEONET sites. To assess the quality of SoftBank's GNSS data, we first analyzed data from Miyagi Prefecture and evaluated the stability of the coordinate time series for nine consecutive days during a quiet (interseismic) period. The calculated standard deviations were approximately the same for both networks. Furthermore, we calculated the displacement between September 2020 and March 2021. The results reveal that almost all SoftBank sites showed a consistent displacement with their surrounding GEONET sites. Next, we analyzed the coseismic deformation associated with the off-Fukushima earthquake (M_JMA 7.3) on February 13, 2021, in both static and kinematic modes. We obtained a westward coherent displacement along the coastline in both networks, although several outliers were observed for the SoftBank sites. Based on these initial assessments, we conclude that these private sector GNSS sites are useful for crustal deformation monitoring with appropriate data quality control. Graphical Abstract
• Investigation of Ionospheric Response to June 2009 Sarychev Peak Volcano Eruption

  Shestakov, N, A. Orlyakovskiy, N. Perevalova, N. Titkov, D. Chebrov, M. Ohzono, H. Takahashi

  Remote Sensing 13 (4) 638 - 638 2021/02 [Refereed][Not invited]
   

  Global Navigation Satellite Systems have been extensively used to investigate the ionosphere response to various natural and man-made phenomena for the last three decades. However, ionospheric reaction to volcano eruptions is still insufficiently studied and understood. In this work we analyzed the ionospheric response to the 11–16 June 2009 VEI class 4 Sarychev Peak volcano eruption by using surrounding Russian and Japanese GPS networks. Prominent covolcanictotal electron content (TEC)ionospheric disturbances (CVIDs) with amplitudes and periods ranged between 0.03–0.15 TECU and 2.5–4.5 min were discovered for the three eruptive events occurred at 18:51 UT, 14 June; at 01:15 and 09:18 UT, 15 June 2009. The estimates of apparent CVIDs velocities vary within 700–1000 m/s in the far-field zone (300–900 km to the southwest from the volcano) and 1300–1800 m/s in close proximity toSarychev Peak. The characteristics of the observed TEC variations allow us to attribute them to acoustic mode. The south-southwestward direction is preferred for CVIDs propagation. We concluded that the ionospheric response to a volcano eruption is mainly determined by a ratio between explosion strength and background ionization level. Some evidence of secondary (F2-layer) CVIDs’ source eccentric location were obtained.
• Focal mechanisms and the stress field in the aftershock area of the 2018 Hokkaido Eastern Iburi earthquake (MJMA = 6.7)

  Yuki Susukida, Kei Katsumata, Masayoshi Ichiyanagi, Mako Ohzono, Hiroshi Aoyama, Ryo Tanaka, Masamitsu Takada, Teruhiro Yamaguchi, Kazumi Okada, Hiroaki Takahashi, Shin’ichi Sakai, Satoshi Matsumoto, Tomomi Okada, Toru Matsuzawa, Hiroki Miyamachi, Shuichiro Hirano, Yoshiko Yamanaka, Shinichiro Horikawa, Masahiro Kosuga, Hiroshi Katao, Yoshihisa Iio, Airi Nagaoka, Noriko Tsumura, Tomotake Ueno

  Earth, Planets and Space 73 (1) 2021/01 [Refereed]
   

  The tectonic stress field was investigated in and around the aftershock area of the Hokkaido Eastern Iburi earthquake (M_JMA = 6.7) occurred on 6 September 2018. We deployed 26 temporary seismic stations in the aftershock area for approximately 2 months and located 1785 aftershocks precisely. Among these aftershocks, 894 focal mechanism solutions were determined using the first-motion polarity of P wave from the temporary observation and the permanent seismic networks of Hokkaido University, Japan Meteorological Agency (JMA), and High Sensitivity Seismograph Network Japan (Hi-net). We found that (1) the reverse faulting and the strike-slip faulting are dominant in the aftershock area, (2) the average trend of P- and T-axes is 78° ± 33° and 352° ± 51°, respectively, and (3) the average plunge of P- and T-axes is 25° ± 16° and 44° ± 20°, respectively: the P-axis is close to be horizontal and the T-axis is more vertical than the average of the P-axes. We applied a stress inversion method to the focal mechanism solutions to estimate a stress field in the aftershock area. As a result, we found that the reverse fault type stress field is dominant in the aftershock area. An axis of the maximum principal stress (σ₁) has the trend of 72° ± 7° and the dipping eastward of 19° ± 4° and an axis of the intermediate principal stress (σ₂) has the trend of 131° ± 73° and the dipping southward of 10° ± 9°, indicating that both of σ₁- and σ₂-axes are close to be horizontal. An axis of the minimum principal stress (σ₃) has the dipping westward of 67° ± 6° that is close to be vertical. The results strongly suggest that the reverse-fault-type stress field is predominant as an average over the aftershock area which is in the western boundary of the Hidaka Collision Zone. The average of the stress ratio R = (σ₁ − σ₂)/(σ₁ − σ₃) is 0.61 ± 0.13 in the whole aftershock area. Although not statistically significant, we suggest that R decreases systematically as the depth is getting deep, which is modeled by a quadratic polynomial of depth.
• Urgent Joint Seismic Observation Data of the 2016 Kumamoto Earthquakes

  志藤あずさ, 志藤あずさ, 光岡郁穂, 松本聡, 松島健, 相澤広記, 清水洋, 内田和也, 神薗めぐみ, 神薗めぐみ, 手操佳子, 手操佳子, 中元真美, 中元真美, 宮町凛太郎, 宮町凛太郎, 一柳昌義, 大園真子, 岡田和見, 勝俣啓, 高田真秀, 高橋浩晃, 谷岡勇市郎, 山口照寛, 小菅正裕, 東龍介, 内田直希, 江本賢太郎, 太田雄策, 岡田知己, 海田俊輝, 小園誠史, 鈴木秀市, 高木涼太, 出町知嗣, 中原恒, 中山貴史, 平原聡, 松澤暢, 三浦哲, 山本希, 今西和俊, 内出崇彦, 吉見雅行, 青井真, 浅野陽一, 上野友岳, 藤田英輔, 阿部英二, 飯高隆, 飯高隆, 岩崎貴哉, 岩崎貴哉, 加藤愛太郎, 蔵下英司, 酒井慎一, 酒井慎一, 椎名高裕, 椎名高裕, 芹澤正人, 田中伸一, 中川茂樹, 平田直, 平田直, 増田正孝, 宮川幸治, 八木健夫, 渡邉篤志, 後藤和彦, 伊藤武男, 奥田隆, 寺川寿子, 堀川信一郎, 前田裕太, 松廣健二郎, 山中佳子, 渡辺俊樹, 飯尾能久, 片尾浩, 加納靖之, 加納靖之, 津田寛大, 三浦勉, 村本智也, 村本智也, 山下裕亮, 大久保慎人, 山品匡史, 大倉敬宏, 中尾茂, 平野舟一郎, 宮町宏樹, 八木原寛

  地震 73 (Nov) 149 - 157 0037-1114 2020/10/27 [Refereed]
  
• The influence of elastic thickness non-uniformity on viscoelastic crustal response to magma emplacement: Application to the Kutcharo caldera, eastern Hokkaido, Japan

  Tadashi Yamasaki, Hiroaki Takahashi, Mako Ohzono, Tim J Wright, Tomokazu Kobayashi

  Geophysical Journal International 224 (1) 701 - 718 0956-540X 2020/09/23 [Refereed][Not invited]
   

  An elastic layer plays an important role in deformation of the crust. At active volcanoes, its thickness would be effectively thinned by a higher geothermal gradient, particularly in a region beneath which magmatic activity is relatively high. This study examines the influence of elastic thickness non-uniformity on viscoelastic crustal deformation by magma emplacement. A 3-D linear Maxwell viscoelastic model is employed, in which an elastic layer underlain by a viscoelastic layer with a spatially uniform viscosity is thinned to be hi in the volcano centre, compared with hi + Δh in the peripheral regions, and a sill-like magma emplacement occurs in the upper layer beneath the centre. It is found that the post-emplacement viscoelastic subsidence is diminished or enhanced by the elastic thickness non-uniformity, depending on whether or not the horizontal width of the magma emplacement (ωs) is greater than the horizontal width (ωe) over which the elastic layer is thinner. The available signature of the non-uniformity is explored by comparison with a model that has a spatially uniform elastic thickness of hi. If an apparent viscosity (ηa) of the uniform elastic thickness model is adjusted so that the difference in post-emplacement subsidence is minimised at the deformation centre, the non-uniformity appears in the overall deformation field as a displacement anomaly over the perimeter of the sill in which viscoelastic subsidence is greater for the non-uniform model. The anomaly is, however, by no more than the magnitude of ∼15 per cent of the maximal syn-emplacement uplift, though ηa is necessarily modified to be ∼0.2–10 times the non-uniform model viscosity (ηc). If ωe is larger than a few times ωs, a weak signature is no longer expected in the deformation field, and ηa is not significantly deviated from ηc. Since the signature appears so faintly in a displacement field, the InSAR data in the Kutcharo caldera for a period from 13 August 1993 to 9 June 1998 do not allow us to capture the non-uniformity. However, it can be concluded that if ωe beneath the caldera is comparable with or greater than the topographic caldera diameter (ωc) as implied by the spatial variation of the geothermal gradient, the non-uniformity has no significant influence. Otherwise, if ωe < ωc, the non-uniformity influences the estimation of the crustal viscosity, but does not affect the overall deformation field. The elastic thickness non-uniformity can be theoretically captured in the deformation field, but in practice, its influence, particularly on estimating crustal viscosity, cannot be properly inferred without other geophysical data such as the geothermal gradient in and around the caldera.
• Spatiotemporal Change in the Stress State Around the Hypocentral Area of the 2016 Kumamoto Earthquake Sequence

  Ayaho Mitsuoka, Azusa Shito, Satoshi Matsumoto, Yusuke Yamashita, Manami Nakamoto, Shin‐ichi Sakai, Yoshihisa Iio, Hiroshi Shimizu, Kazuhiko Goto, Tomomi Okada, Mako Ohzono, Yoshiko Yamanaka, Masahiro Kosuga, Masayuki Yoshimi, Youichi Asano

  Journal of Geophysical Research: Solid Earth 125 (9) 2169-9313 2020/09 [Refereed][Not invited]
   

  For understanding the physical condition of earthquake generation, we estimated the deviatoric stress fields and fault planes of the large earthquakes in the hypocentral area of the 2016 Kumamoto earthquake sequence, central Kyushu, Japan. We analyzed precise hypocenters and their focal mechanism tensors from 1993 to 2017 and found the complex fault planes of the largest foreshock and the mainshock during the sequence. The faults of large earthquakes could not be detected from the preceding high seismic activity in the area to the mainshock. The analyses of the deviatoric stress tensors obtained from pre- and post-sequence seismic moment tensor data revealed the temporal change in the deviatoric stress field at the vicinity of the hypocenters of the largest foreshock and the mainshock. Because of this temporal change, we found that the stress level of the deviatoric stress field in this region is the same level as the co-seismic stress change caused by the two large earthquakes. We attempted to estimate the differential stress at the region using a new method, which can be applied to the heterogeneous stress fields. The average value of the estimated differential stresses in the region was 15.4 +/- 10 MPa. The rotation of the principal stress axes and the low differential stress are important information to understand the physical processes of the earthquake generation and the state of the crustal stress.
• Subsidence at lava dome of Tarumae volcano as revealed by ALOS-2/PALSAR-2 InSAR(2015-2019)

  Satoshi Fuwa, Shohei Narita, Mako Ohzono, Makoto Murakami

  Geophysical Bulletin of Hokkaido University 北海道大学大学院理学研究院 83 (83) 71 - 83 0439-3503 2020/03 [Not refereed][Not invited]
  
• Spatiotemporal crustal strain distribution around eastern Hokkaido measured by GEONET

  Mako Ohzono

  Geophysical bulletin of Hokkaido University 83 85 - 96 2020/03 [Not refereed][Not invited]
  
• 絶対重力計との比較による超伝導重力計のスケールファクターの推定 : 2019年9月北海道大学弟子屈観測所において

  名和, 一成, 今西, 祐一, 西山, 竜一, 高橋, 浩晃, 大園, 真子, 岡田, 和見, 山口, 照寛, 本多, 亮

  北海道大学地球物理学研究報告 83 97 - 101 2020/03 [Not refereed][Not invited]
  
• 2019年に発生した札幌市西区福井・平和付近の地震活動

  一柳, 昌義, 大園, 真子, 高田, 真秀, 高橋, 浩晃

  北海道大学地球物理学研究報告 83 1 - 7 2020/03 [Not refereed][Not invited]
  
• Crustal deformation of northeastern China following the 2011 Mw9.0 Tohoku, Japan earthquake estimated from GPS observations: Strain heterogeneity and seismicity

  Meng, G, X. Su, W. Wu, N. Shestakov, H. Takahashi, M. Ohzono, M. Gerasimenko

  Remote Sensing 11 3029  2019/12 [Refereed][Not invited]
  
• Estimation of convergence boundary location and velocity between tectonic plates in northern Hokkaido inferred by GNSS velocity data

  Ito, C, H. Takahashi, M. Ohzono

  Earth Planets Space 71 (85) 2019/08 [Refereed][Not invited]
  
• The 2018 Hokkaido Eastern Iburi earthquake (MJMA = 6.7) was triggered by a strike-slip faulting in a stepover segment: Insights from the aftershock distribution and the focal mechanism solution of the main shock

  Katsumata, K, M. Ichiyanagi, M. Ohzono, H. Aoyama, R. Tanaka, M. Takada, T. Yamaguchi, K. Okada, H. Takahashi, S. Sakai, S. Matsumoto, T. Okada, T. Matsuzawa, S. Hirano, T. Terakawa, S. Horikawa, M. Kosuga, H. Katao, Y. Iio, A. Nagaoka, N. Tsumura, T. Ueno

  Earth Planets Space 71 53  1880-5981 2019/05 [Refereed][Not invited]
   

  The Hokkaido Eastern Iburi earthquake (M-JMA=6.7) occurred on September 6, 2018, in the Hokkaido corner region where the Kurile and northeastern Japan island arcs meet. We relocated aftershocks of this intraplate earthquake immediately after the main shock by using data from a permanent local seismic network and found that aftershock depths were concentrated from 20 to 40km, which is extraordinarily deep compared with other shallow intraplate earthquakes in the inland area of Honshu and Kyushu, Japan. Further, we found that the aftershock area consists of three segments. The first segment is located in the northern part of the aftershock area, the second segment lies in the southern part, and the third segment forms a stepover between the other two segments. The hypocenter of the main shock, from which the rupture initiated, is located on the stepover segment. The centroid moment tensor solution for the main shock indicates a reverse faulting, whereas the focal mechanism solution determined by using the first-motion polarity of the P wave indicates strike-slip faulting. To explain this discrepancy qualitatively, we present a model in which the rupture started as a small strike-slip fault in the stepover segment of the aftershock area, followed by two large reverse faulting ruptures in the northern and southern segments.
• Spatiotemporal crustal strain distribution around the Ishikari-Teichi-Toen fault zone estimated from global navigation satellite system data

  Mako Ohzono, Hiroaki Takahashi, Chihiro Ito

  Earth Planets and Space 71 50  2019/04 [Refereed][Not invited]
  
• Tiltmerer observation in Avachinsky volcano, Kamchatka, Russia

  Takahashi, H, H. Aoyama, M. Ohzono, R. Tanaka, C. Ito, S. Watanabe, T. Matsushima, Y. Yamashita, H. Miyamachi, S. Okuyama, E. Gordeev, Y. Muraviyev, K. Maguskin, N. Malik, I. Minorov, D. Chebrov

  Geophysical Bulletin of Hokkaido University 82 11 - 18 2019/03 [Not refereed][Not invited]
  
• Seismic activity associated with the 2014 Shiraoi earthquake（MJMA 5.6）in middle east Iburi region, Hokkaido (Hypocenter data file)

  ICHIYANAGI Masayoshi, SHESTAKOV Nikolay V., OKUYAMA Satoshi, OHZONO Mako, KASAHARA Minoru, TAKAHASHI Hiroaki

  Geophysical bulletin of Hokkaido University 北海道大学大学院理学研究院 (81) 1 - 1 0439-3503 2018/03/19
• Measurements for vertical gradient of gravity on active crater region in Tokachi-dake volcano, Hokkaido

  TAKAHASHI Hiroaki, Mako OHZONO Mako, ICHIYANAGI Masayoshi, YAMAGUCHI Teruhiro, OKADA Kazumi, SAITO Kazuma, FUWA Satoshi, ITO Chihiro, OKAZAKI Noritoshi, TAKAGI Akimichi, HONDA Ryo

  Geophysical bulletin of Hokkaido University 北海道大学大学院理学研究院 81 (81) 57 - 60 2018/03 [Not refereed][Not invited]
  
• Absolute gravity measurements in caldera area of eastern Hokkaido

  NAWA Kazunari, MIYAKAWA Ayumu, YAMASAKI Tadashi, MOCHIZUKI Kazuma, TAKAHASHI Hiroaki, OHZONO Mako, OKADA Kazumi, OKA Daisuke, OKAZAKI Noritoshi, HONDA Ryo

  Geophysical bulletin of Hokkaido University 北海道大学大学院理学研究院 81 (81) 11 - 16 0439-3503 2018/03 [Not refereed][Not invited]
  
• GNSS観測に基づく2016年熊本地震（M7.3）の余効変動時系列解析による九州地方の粘性構造の推定

  不破智志, 大園真子

  北大地物報告 81 45 - 55 2018/03 [Not refereed][Not invited]
  
• 2014年7月8日に発生した北海道白老町付近（胆振地方中東部）の地震（MJMA 5.6）について

  一柳昌義, シェスタコフ ニコライ, 奥山哲, 大園真子, 笠原稔, 高橋浩晃

  北大地物報告 81 17 - 26 2018/03 [Not refereed][Not invited]
  
• Prestate of Stress and Fault Behavior During the 2016 Kumamoto Earthquake (M7.3)

  Satoshi Matsumoto, Yusuke Yamashita, Manami Nakamoto, Masahiro Miyazaki, Shinichi Sakai, Yoshihisa Iio, Hiroshi Shimizu, Kazuhiko Goto, Tomomi Okada, Mako Ohzono, Toshiko Terakawa, Masahiro Kosuga, Masayuki Yoshimi, Youichi Asano

  Geophysical Research Letters 45 (2) 637 - 645 1944-8007 2018/01/28 [Refereed][Not invited]
   

  Fault behavior during an earthquake is controlled by the state of stress on the fault. Complex coseismic fault slip on large earthquake faults has recently been observed by dense seismic networks, which complicates strong motion evaluations for potential faults. Here we show the three-dimensional prestress field related to the 2016 Kumamoto earthquake. The estimated stress field reveals a spatially variable state of stress that forced the fault to slip in a direction predicted by the “Wallace and Bott Hypothesis.” The stress field also exposes the pre-condition of pore fluid pressure on the fault. Large coseismic slip occurred in the low-pressure part of the fault. However, areas with highly pressured fluid also showed large displacement, indicating that the seismic moment of the earthquake was magnified by fluid pressure. These prerupture data could contribute to improved seismic hazard evaluations.
• Present-day strain accumulation in the Liupan Shan area, northeastern margin of the Tibetan Plateau by GPS observations

  G. Meng, X. Su, W. Xu, C-H. Chen, K-C. Cheng, S. Wen, T-K. Yeh, P. Li, M. Ohzono, H. Takahashi

  Terrestrial, Atmospheric and Oceanic sciences journal 29 2018 [Refereed][Not invited]
  
• Gravity changes observed around the 62-II crater, Tokachi-dake volcano by precise gravity survey

  Okazaki N., Takahashi R., Takahashi H., Ohzono M., Ichiyanagi M., Yamaguchi T., Okada K., Honda R., Takagi A.

  PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 特定非営利活動法人 日本火山学会 2017 (0) 158 - 158 2433-5320 2017
• Rheological structure beneath NE Japan inferred fromcoseismic strain anomalies associated with the 2011 Tohoku-oki earthquake (MW9.0)

  Yasuo Yabe, Jun Muto, Mako Ohzono, Yusaku Ohta, Takeshi Iinuma

  International Association of Geodesy Symposia 145 63 - 71 0939-9585 2017 [Refereed][Not invited]
   

  © Springer International Publishing Switzerland 2015. Strain concentration zones (SCZs), in which the E–W contraction under a slow tectonic loading is larger than the surrounding area, in NE Japan have been attributed to low viscosity anomalies (LVAs) in their lower crust. The 2011 Tohoku-oki earthquake (Mw9.0) induced a stepwise stress change over NE Japan. The coseismic E–W extension in the SCZ along the Ou backbone Range (OBR) was smaller than theoretical one, whereas it was larger in the forearc SCZ (FSCZ). This suggests variation in rheological structure beneath the SCZs. We numerically evaluated responses of variety of rheological models to the tectonic slow loading and the coseismic instantaneous unloading. A model with a viscoelastic upper crust, which is caused by high temperature relating to magmatic processes along volcanic front, below the OBR can reproduce the observed deformations in the OBR. The surface deformations in the FSCZ were explained as enhanced deformations of thick, compliant sediment. The viscoelasticity in the upper crust was not allowed beneath the FSCZ. LVA in the lower crust was not essential to reproduce the preseismic and the coseismic deformation anomalies in the FSCZ. However, the postseismic deformation was strongly affected by the existence of LVA in the lower crust. Precise observations of the postseismic deformations should provide key clues to elucidate the rheological structure beneath the FSCZ.
• 2015年に発生した阿寒湖付近の地震（MJMA5.0），北海道大学地球物理学研究

  一柳昌義, 高橋浩晃, 山口照寛, 岡田和見, 大園眞子, 岡崎紀俊

  北海道大学地球物理学研究 69 1 - 8 2016 [Not refereed][Not invited]
  
• Behavior of a GEONET Pillar Associated with a Shallow Earthquake in Eastern Hokkaido on June 4, 2015

  Ohzono Mako, Takahashi Hiroaki

  Journal of the Geodetic Society of Japan 日本測地学会 62 (1) 21 - 27 0038-0830 2016 [Refereed][Not invited]
   

  Behavior and instability of a GEONET pillar under strong seismic ground motion was evaluated. Coseismic displacement at the 0513 GEONET site due to a M5.0 local earthquake with 5- intensity showed four times larger value than predicted one from theoretical estimation. Inclination of the pillar due to strong seismic ground shaking was a candidate of the tilt change because little tilt change was expected from earthquake faulting. Corrected coseismic displacement was well consistent with that from theoretical value, and suggested unstable behavior of this pillar by strong ground shaking. High correlation between temperature and coordinate fluctuations for three years data also might request correlation of pillar movement for GNSS coordinate time series using tiltmeter data.

• Earthquake swarm around Nakagawa town, northern Hokkaido in 2012

  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]
   

  An earthquake swarm begun at 15 July 2012 in Nakagawa town of northern Hokkaido. The largest earthquake with MJMA4.3 occurred on 16 July 2012. We carried out temporal seismic observation with seven stations from 18 July 2012 to the last October 2012. Hypocenters were calculated using the Double-Difference hypocenter determination procedure with a local one dimensional P-wave velocity structure. Precise hypocenter data indicated that epicenters were distributed in very narrow area of 2 km×2 km with shallow depth from 4 km to 7 km. Earthquakes after middle of August occurred only in southern part of the region and depth had got shallower with time. Hypocenters indicated no clear alignment in consistent with any nodal planes of major earthquakes. An independent hypocenter cluster with shallower than 2 km was observed above the main activity area. A slow slip event (SSE) with Mw 5.4 coincidentally detected by GNSS crustal deformation data during the swarm. This swarm was situated at the southeastern end of the fault of SSE. This fact suggested that seismic swarm might triggered SSE or was induced by SSE.
• P41 Seismic Activity of Akan-Teshikaga region, Eastern Hokkaido

  ICHIYANAGI Masayoshi, TAKAHASHI Hiroaki, YAMAGUCHI Teruhiro, OKADA Kazumi, TAKADA Masamitsu, OHZONO Mako, OKAZAKI Noritoshi

  PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 特定非営利活動法人 日本火山学会 2015 139 - 139 2015
• P52 Strain field around Kussharo Caldera, eastern Hokkaido, measured by dense GPS observation network

  Ohzono Mako, Takahashi Hiroaki, Ichiyanagi Masayoshi

  PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN 特定非営利活動法人 日本火山学会 2015 150 - 150 2015
• An intraplate slow earthquake observed by a dense GPS network in Hokkaido, northernmost Japan

  Mako Ohzono, Hiroaki Takahashi, Masayoshi Ichiyanagi

  GEOPHYSICAL JOURNAL INTERNATIONAL 200 (1) 144 - 148 0956-540X 2015/01 [Refereed][Not invited]
   

  An intraplate slow earthquake was detected in northernmost Hokkaido, Japan, by a dense network of the global navigation satellite system. Transient abnormal acceleration of <12 mm was observed during the period 2012 July to 2013 January (similar to 5.5 months) at several sites. The spatial displacement distribution suggests that a localized tectonic event caused localized deformation. Estimated fault parameter indicates very shallow-dip reverse faulting in the uppermost crust, with a total seismic moment of 1.75E + 17 N m (M-w 5.4). This fault geometry is probably consistent with detachment structure indicated by geological studies. A simultaneous earthquake swarm with the maximum magnitude M4.1 suggests a possibility that the slow slip triggered the seismic activity for unknown reasons. This slow earthquake is slower than its moment would indicate, with a duration-magnitude scaling relationship unlike either regular earthquakes or subduction slow slip events. This result indicates that even if the area is under different physical property from subduction zones, slow earthquake can occur by some causes. Slow earthquakes exist in remote regions away from subduction zones and might play an important role in strain release and tectonic activity.
• Modeling of coseismic crustal movements initiated by the May 24, 2013, M (w)=8.3 Okhotsk deep focus earthquake

  N. V. Shestakov, M. Ohzono, H. Takahashi, M. D. Gerasimenko, V. G. Bykov, E. I. Gordeev, V. N. Chebrov, N. N. Titkov, S. S. Serovetnikov, N. F. Vasilenko, A. S. Prytkov, A. A. Sorokin, M. A. Serov, M. N. Kondratyev, V. V. Pupatenko

  DOKLADY EARTH SCIENCES 457 (2) 976 - 981 1028-334X 2014/08 [Refereed][Not invited]
   

  The Okhotsk deep focus earthquake (M (w) = 8.3), the largest in the history of instrumental seismology, occurred on May 24, 2013, at 05:45 UTC in the Sea of Okhotsk near the western coast of the Kamchatka Peninsula. For the first time we have succeeded in catching the field of horizontal and vertical coseismic offsets generated by a strong deep seismic event, and investigating its characteristics using continuous GPS measurements. Based on these data and taking into account the seismological information, we have developed a dislocation model of the Okhotsk deep focus earthquake.
• The 2012 Earthquake Swarm in Nigorikawa Caldera, Hokkaido

  一柳昌義, 笠原稔, 高橋浩晃, 岡崎紀俊, 高橋良, 大園真子

  北海道大学地球物理学研究報告 北海道大学大学院理学研究院 77 (77) 5 - 14 0439-3503 2014 [Not refereed][Not invited]
   

  An earthquake swarm begun at the end of January, 2012 and the activity reached a peak in middle February, then gradually decreased by the end of April, in the Nigorikawa caldera, Hokkaido. The largest earthquake was the MJMA3.6 event which occurred on 15 February 2012 with maximum intensity 3．Temporal seismic observation with two stations carried out from 20 February to 9 April in the caldera. Detailed hypocenter distribution estimated by using both data temporal and secular observations shows two clusters, one of them is aligned along the northern caldera wall and another is located at eastern outside of caldera. Strike of alignment epicenter of the north cluster shows NE-SW direction, which is in good agreement with one of the nodal plane of focal mechanism of the largest event.
• Two-dimensional viscosity structure of the northeastern Japan islands arc-trench system

  Jun Muto, Bunichiro Shibazaki, Yoshihiro Ito, Takeshi Iinuma, Mako Ohzono, Takumi Matsumoto, Tomomi Okada

  GEOPHYSICAL RESEARCH LETTERS 40 (17) 4604 - 4608 0094-8276 2013/09 [Refereed][Not invited]
   

  Two-dimensional viscosity profiles were constructed for the northeastern Japan islands arc-trench system covering the source area of the 2011 Tohoku-Oki earthquake. From seismologically determined models of lithospheric structure, experimentally derived constitutive laws of various rocks, and densely measured geothermal gradient data, we have predicted the steady state effective viscosity across the subduction zone. The profile reveals strong lateral viscosity gradients both parallel and normal to the trench axis. The detailed viscosity structures presented here contribute to accurate evaluation of viscoelastic relaxation components when modeling geodetically measured postseismic deformation at high spatial and temporal resolution.
• Rheological structure of the NE Japan island arc-trench system and viscoelastic stress relaxation after the 2011 Tohoku Oki Earthquake

  Jun Muto, Bunichiro Shibazaki, Yoshihiro Ito, Takeshi Iinuma, Mako Ohzono, Takumi Matsumoto, Tomomi Okada

  Proceeding of The 6th International Symposium on In-situ Rock Stress 54  2013/08/01 [Refereed][Not invited]
  
• Episodic slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake

  Yoshihiro Ito, Ryota Hino, Motoyuki Kido, Hiromi Fujimoto, Yukihito Osada, Daisuke Inazu, Yusaku Ohta, Takeshi Iinuma, Mako Ohzono, Satoshi Miura, Masaaki Mishina, Kensuke Suzuki, Takeshi Tsuji, Juichiro Ashi

  TECTONOPHYSICS 600 14 - 26 0040-1951 2013/07 [Refereed][Not invited]
   

  We describe two transient slow slip events that occurred before the 2011 Tohoku-Oki earthquake. The first transient crustal deformation, which occurred over a period of a week in November 2008, was recorded simultaneously using ocean-bottom pressure gauges and an on-shore volumetric strainmeter; this deformation has been interpreted as being an M6.8 episodic slow slip event. The second had a duration exceeding 1 month and was observed in February 2011, just before the 2011 Tohoku-Oki earthquake; the moment magnitude of this event reached 7.0. The two events preceded interplate earthquakes of magnitudes M6.1 (December 2008) and M7.3 (March 9, 2011), respectively; the latter is the largest foreshock of the 2011 Tohoku-Oki earthquake. Our findings indicate that these slow slip events induced increases in shear stress, which in turn triggered the interplate earthquakes. The slow slip event source area on the fault is also located within the downdip portion of the huge-coseismic-slip area of the 2011 earthquake. This demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault, suggesting that the faults undergo slip in slow slip events can also rupture seismically. (C) 2012 Elsevier B.V. All rights reserved.
• Spatiotemporal strain distribution based on GPS network in Hokkaido induced by the 2011 off the Pacific coast of Tohoku Earthquake (Mw9.0)

  大園 真子

  北海道大学地球物理学研究報告 北海道大学大学院理学研究院 (76) 97 - 110 0439-3503 2013/03 

  Wide and large coseismic displacement field around Tohoku region, northeastern Japan,are induced by the 2011 off the Pacific coast of Tohoku Earthquake. Because their effectis confirmable not only in Tohoku region, but also Hokkaido, I focus on the coseismic andpostseismic strain field in Hokkaido using nationwide GPS network. A remarkable coseismicdeformation is observed around southwestern Hokkaido, and the coseismic strain distribution showsalso large extension with NNW-SSE direction （～ 0.6ppm）. Published fault models basicallyexplain this coseismic deformation pattern. The displacement field during one year after theearthquake shows significant effect of postseismic deformation especially in the western part ofHokkaido. Along the Pacific coast, which parallels to Kuril trench, two different patterns appearrelative to the interseismic period; smaller displacement in the eastern part （Erimo to Kushiro） ,and approximately same displacement in the western part （Kushiro to Nemuro） . The shorteningstrain toward plate convergence direction is large in both interseismic and postseismic periodsat the eastern part. It suggests that the interplate coupling around eastern Hokkaido has stillcontinued. The relationship between postseismic strain field and shallow seismicity after the 2011earthquake does not appear clearly at present.
• Geodetic constraints on afterslip characteristics following the March 9, 2011, Sanriku-oki earthquake, Japan

  Yusaku Ohta, Ryota Hino, Daisuke Inazu, Mako Ohzono, Yoshihiro Ito, Masaaki Mishina, Takeshi Iinuma, Junichi Nakajima, Yukihito Osada, Kensuke Suzuki, Hiromi Fujimoto, Kenji Tachibana, Tomotsugu Demachi, Satoshi Miura

  GEOPHYSICAL RESEARCH LETTERS 39 L16304  0094-8276 2012/08 [Refereed][Not invited]
   

  A magnitude 7.3 foreshock occurred at the subducting Pacific plate interface on March 9, 2011, 51 h before the magnitude 9.0 Tohoku earthquake off the Pacific coast of Japan. We propose a coseismic and postseismic afterslip model of the magnitude 7.3 event based on a global positioning system network and ocean bottom pressure gauge sites. The estimated coseismic slip and afterslip areas show complementary spatial distributions; the afterslip distribution is located up-dip of the coseismic slip for the foreshock and northward of hypocenter of the Tohoku earthquake. The slip amount for the afterslip is roughly consistent with that determined by repeating earthquake analysis carried out in a previous study. The estimated moment release for the afterslip reached magnitude 6.8, even within a short time period of 51h. A volumetric strainmeter time series also suggests that this event advanced with a rapid decay time constant compared with other typical large earthquakes. Citation: Ohta, Y., et al. (2012), Geodetic constraints on afterslip characteristics following the March 9, 2011, Sanriku-oki earthquake, Japan, Geophys. Res. Lett., 39, L16304, doi:10.1029/2012GL052430.
• Coseismic slip distribution of the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0) refined by means of seafloor geodetic data

  T. Iinuma, R. Hino, M. Kido, D. Inazu, Y. Osada, Y. Ito, M. Ohzono, H. Tsushima, S. Suzuki, H. Fujimoto, S. Miura

  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 117 B07409  2169-9313 2012/07 [Refereed][Not invited]
   

  On 11 March 2011, the devastating M9.0 Tohoku Earthquake occurred on the interface of the subducting Pacific plate, and was followed by a huge tsunami that killed about 20,000 people. Several geophysical studies have already suggested that the very shallow portion of the plate interface might have played an important role in producing such a large earthquake and tsunami. However, the sparsity of seafloor observations leads to insufficient spatial resolution of the fault slip on such a shallow plate interface. For this reason, the location and degree of the slip has not yet been estimated accurately enough to assess future seismic risks. Thus, we estimated the coseismic slip distribution based on terrestrial GPS observations and all available seafloor geodetic data that significantly improve the spatial resolution at the shallow portion of the plate interface. The results reveal that an extremely large (greater than 50 m) slip occurred in a small (about 40 km in width and 120 km in length) area near the Japan Trench and generated the huge tsunami. The estimated slip distribution and a comparison of it with the coupling coefficient distribution deduced from the analysis of the small repeating earthquakes suggest that the 2011 Tohoku Earthquake released strain energy that had accumulated over the past 1000 years, probably since the Jogan Earthquake in 869. The accurate assessments of seismic risks on very shallow plate interfaces in subduction zones throughout the world can be obtained by improving the quality and quantity of seafloor geodetic observations.
• Quasi real-time fault model estimation for near-field tsunami forecasting based on RTK-GPS analysis: Application to the 2011 Tohoku-Oki earthquake (M-w 9.0)

  Yusaku Ohta, Tatsuya Kobayashi, Hiroaki Tsushima, Satoshi Miura, Ryota Hino, Tomoji Takasu, Hiromi Fujimoto, Takeshi Iinuma, Kenji Tachibana, Tomotsugu Demachi, Toshiya Sato, Mako Ohzono, Norihito Umino

  JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 117 2169-9313 2012/02 [Refereed][Not invited]
   

  Real-time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales, because the measured permanent displacement directly gives the true earthquake size (seismic moment, M-w) information, which in turn, provides tsunami forecasting. We have developed an algorithm to detect/estimate static ground displacements due to earthquake faulting from real-time kinematic GPS (RTK-GPS) time series. The new algorithm identifies permanent displacements by monitoring the difference of a short-term average (STA) to a long-term average (LTA) of the GPS time series. We assessed the noise property and precision of the RTK-GPS time series with various baseline length conditions and orbits and discerned that the real-time ephemerides based on the International GNSS Service (IGS) are sufficient for crustal deformation monitoring with long baselines up to similar to 1,000 km. We applied the algorithm to data obtained in the 2011 off the Pacific coast of Tohoku earthquake (M-w 9.0) to test the possibility of coseismic displacement detections, and further, we inverted the obtained displacement fields for a fault model; the inversion estimated a fault model with M-w 8.7, which is close to the actual M-w of 9.0, within five minutes from the origin time. Once the fault model is estimated, tsunami waveforms can be immediately synthesized using pre-computed tsunami Green's functions. The calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights, suggesting that the RTK-GPS data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations.
• Analysis of the far-field crustal displacements caused by the 2011 Great Tohoku earthquake inferred from continuous GPS observations

  Nikolay V. Shestakov, Hiroaki Takahashi, Mako Ohzono, Alexander S. Prytkov, Victor G. Bykov, Mikhail D. Gerasimenko, Margarita N. Luneva, Grigory N. Gerasimov, Andrey G. Kolomiets, Vladimir A. Bormotov, Nikolay F. Vasilenko, Jeongho Baek, Pil-Ho Park, Mikhail A. Serov

  TECTONOPHYSICS 524 76 - 86 0040-1951 2012/02 [Refereed][Not invited]
   

  Small coseismic offsets detectable using GPS techniques were found more than 2300 km away from the Great Tohoku 2011 earthquake epicenter. Area of the most intense far-field co- and postseismic deformations with the maximum offset values exceeding 40 and 18 mm, respectively, extends westward from Honshu Island to the Korean Peninsula, northeastern China and southern Far East Russia. Sakhalin Island does not exhibit notable displacements caused by the earthquake, in contrast to the adjacent territories. A rectangular fault model with uniform slip was developed based on the GPS-detected far-field coseismic displacements using the spherically layered Earth assumption. Both far- and near-field coseismic deformations are generally well described by a single-segment rupture of 200 x 96 km(2), characterized by thrust slip with minor strike-slip component of about 33 m and by the seismic moment value of 1.9.10(22)N.m (Mw=8.8), which roughly constrains the major slip area. The resultant compact fault geometry revealed that the main portion of the seismic moment had been realized in a relatively small-sized rupture segment The sensitivity of far-field GPS data to the major slip area might also be used in the development of a seismically generated giant tsunami warning system. (C) 2011 Elsevier B.V. All rights reserved.
• Strain anomalies induced by the 2011 Tohoku Earthquake (M-w 9.0) as observed by a dense GPS network in northeastern Japan

  Mako Ohzono, Yasuo Yabe, Takeshi Iinuma, Yusaku Ohta, Satoshi Miura, Kenji Tachibana, Toshiya Sato, Tomotsugu Demachi

  EARTH PLANETS AND SPACE 64 (12) 1231 - 1238 1343-8832 2012 [Refereed][Not invited]
   

  We have evaluated an anomalous crustal strain in the Tohoku region, northeastern Japan associated with a step-like stress change induced by the 2011 off the Pacific coast of Tohoku Earthquake (M-w 9.0). Because the source area of the event was extremely large, the gradient of the observed eastward coseismic displacements that accompanied uniform stress change had a relatively uniform EW extension in northeastern Japan. Accordingly, the deformation anomaly, which is determined by subtracting the predicted displacement in a half-space elastic media from the observed displacement, should reflect the inhomogeneity of the rheology, or stiffness, of the crust. The difference of the EW extension anomaly between the forearc and backarc regions possibly indicates a dissimilarity of stiffness, depending on the crustal structure of the Tohoku region. The Ou-backbone range-a strain concentration zone in the interseismic period-shows an extension deficit compared with predictions. A low viscosity in the lower crust probably induced a relatively small extension. Meanwhile, the northern part of the Niigata-Kobe tectonic zone, another strain concentration zone, indicates an excess of extensional field. This is probably caused by a low elastic moduli of the thick sedimentation layer. The detection of strain anomalies in the coseismic period enables a new interpretation of the deformation process at strain concentration zones.
• Geodetic evidence of viscoelastic relaxation after the 2008 Iwate-Miyagi Nairiku earthquake

  Mako Ohzono, Yusaku Ohta, Takeshi Iinuma, Satoshi Miura, Jun Muto

  EARTH PLANETS AND SPACE 64 (9) 759 - 764 1343-8832 2012 [Refereed][Not invited]
   

  Continuous GPS observations, for over two years, detected long-term postseismic deformation after the 2008 Iwate-Miyagi Nairiku earthquake (M-j 7.2). The displacement field exhibits ESE-WNW shortening and subsidence near the focal area. These features are attributed to a viscoelastic relaxation caused by the mainshock. A simple two-layered structural model, which consists of an elastic layer having a thickness of 19.0-23.5 km and an underlying Maxwell viscoelastic layer having a viscosity of 2.4-4.8 x 10(18) Pa s, explains the far-field deformation pattern, which probably reflects the viscoelastic response exclusively. These estimated parameters are consistent with the deeper limit of the seismogenic layer in the upper crust and the previous rheological model in northeastern Japan. However, near-field deformation requires additional sources in order to reproduce the observed postseismic deformation, such as long-term afterslip and/or a complicated response due to the highly heterogeneous structure suggested by seismic tomography studies.
• Rheological profile across the northeastern Japan lithosphere toward precise modeling of the 2011 Tohoku Oki Earthquake

  Muto Jun, Ohzono Mako

  The Journal of the Geological Society of Japan 一般社団法人 日本地質学会 118 (5) 322 - 333 0016-7630 2012 [Refereed][Not invited]
   

  A two-dimensional rheological profile crossing the northeastern Japan arc was created to evaluate and distinguish various styles of post-seismic deformation relating to the 2011 Tohoku-Oki earthquake. The calculated profile is based on recent rock-mechanics studies and geophysical observations that explain observed patterns of geodetic strain accumulation and shallow seismicity prior to the earthquake. Viscosities were then calculated assuming stress-change magnitudes commonly associated with interplate earthquakes. Recently derived flow laws for various rocks and minerals predict the presence of weak zones that developed via processes likely operating in the lithosphere (e.g., partial melting and shear zone development). Strain localization into weak zones explains low viscosity estimates (10¹⁸—10²⁰ Pas) from post-seismic creep after inland earthquake events. Our calculations reveal significant lateral variations in strengths and viscosities across the northeastern Japan arc. These viscoelastic lithospheric structures should be taken into account in order to differentiate viscous relaxation from other post-seismic deformation processes.
• Large intraslab earthquake (2011 April 7, M 7.1) after the 2011 off the Pacific coast of Tohoku Earthquake (M 9.0): Coseismic fault model based on the dense GPS network data

  Yusaku Ohta, Satoshi Miura, Mako Ohzono, Saeko Kita, Takeshi Iinuma, Tomotsugu Demachi, Kenji Tachibana, Takashi Nakayama, Satoshi Hirahara, Syuichi Suzuki, Toshiya Sato, Naoki Uchida, Akira Hasegawa, Norihito Umino

  EARTH PLANETS AND SPACE 63 (12) 1207 - 1211 1343-8832 2011 [Refereed][Not invited]
   

  We propose a source fault model for the 2011, April 7, earthquake (M 7.1) deduced from a dense GPS network. The coseismic displacements obtained by GPS data analysis clearly show the spatial pattern specific to intraslab earthquakes, not only in the horizontal components but also the vertical ones. A rectangular fault with uniform slip was estimated by a non-linear inversion approach. The results indicate that the simple rectangular fault model can explain the overall features of the observations. The amount of moment released is equivalent to M-w 7.17. The hypocenter depth of the main shock estimated by the Japan Meteorological Agency is slightly deeper than the neutral plane between down-dip compression (DC) and down-dip extension (DE) stress zones of the double-planed seismic zone. This suggests that the depth of the neutral plane was deepened by the huge slip of the 2011, M 9.0, Tohoku Earthquake, and the rupture of the thrust M 7.1 earthquake was initiated at that depth, although more investigations are required to confirm this idea. The estimated fault plane has an angle of similar to 60 degrees from the surface of the subducting Pacific plate. It is consistent with the hypothesis that intraslab earthquakes are thought to be a reactivation of the pre-existing hydrated weak zones produced in the bending process of oceanic plates around outer-rise regions.
• Crustal displacements and deformations of the Russian Far East induced by the Tohoku earthquake of March 11, 2011, Mw = 9,0 and their influence on the results of GNSS observations

  Шестаков Н. В, М. Д. Герасименко, M. Охзон

  J. Geodesy and Cartography 8 35 - 43 2011 [Refereed][Not invited]
  
• Coseismic slip distribution of the 2011 off the Pacific coast of Tohoku Earthquake (M 9.0) estimated based on GPS data-Was the asperity in Miyagi-oki ruptured?

  Takeshi Iinuma, Mako Ohzono, Yusaku Ohta, Satoshi Miura

  EARTH PLANETS AND SPACE 63 (7) 643 - 648 1343-8832 2011 [Refereed][Not invited]
   

  We investigated the crustal deformation associated with the 2011 off the Pacific coast of Tohoku Earthquake (M 9.0) that occurred on March 11, 2011, along the plate boundary off Tohoku district, northeastern Japan, based on dense GPS observation. Coseismic displacements due to this event were applied to estimate the causal interplate slip by means of a geodetic inversion analysis. The major slip area is located around the asperities of the 1981 Miyagi-oki (M 7.2) and 2003 Fukushima-oki (M 6.8) earthquakes and the maximum slip is estimated as being up to 35 m. The estimated slip distribution suggests that the asperities of the Miyagi-oki earthquake in 1978 (M 7.4) that had not been ruptured during the Miyagi-oki earthquake in 2005 were ruptured as a part of the main shock fault of the 2011 off the Pacific coast of Tohoku Earthquake.
• Strain accumulation process around the Atotsugawa fault system in the Niigata-Kobe Tectonic Zone, central Japan

  Ohzono, M., Sagiya, T., Hirahara, K., Hashimoto, M., Takeuchi, A., Hoso, Y., Wada, Y., Onoue, K., Ohya, F., Doke, R.

  Geophysical Journal International 184 (3) 977 - 990 2011 [Refereed][Not invited]
  
• Aseismic slow slip on an inland active fault triggered by a nearby shallow event, the 2008 Iwate-Miyagi Nairiku earthquake (Mw6.8)

  T. Iinuma, M. Ohzono, Y. Ohta, S. Miura, M. Kasahara, H. Takahashi, T. Sagiya, T. Matsushima, S. Nakao, S. Ueki, K. Tachibana, T. Sato, H. Tsushima, K. Takatsuka, T. Yamaguchi, M. Ichiyanagi, M. Takada, K. Ozawa, M. Fukuda, Y. Asahi, M. Nakamoto, Y. Yamashita, N. Umino

  GEOPHYSICAL RESEARCH LETTERS 36 L20308  0094-8276 2009/10 [Refereed][Not invited]
   

  Using GPS observations, we have detected an aseismic slip event on the intraplate Dedana Fault that was triggered by the Iwate-Miyagi Nairiku earthquake (Mw6.8, 13 Jun 2008 UTC) on a nearby but separate fault. The observations cannot be satisfactorily explained in terms of either viscoelastic relaxation or poroelastic rebound, and we cannot explain the observed displacement time series without presuming that aseismic slip occurred on the Dedana Fault. This slip was likely triggered by the mainshock stress change. The detection of future such aseismic slip events on intraplate faults is likely to require denser geodetic networks than are currently in operation, but is important for fully characterizing the seismic hazard associated with intraplate earthquakes. Citation: Iinuma, T., et al. (2009), Aseismic slow slip on an inland active fault triggered by a nearby shallow event, the 2008 Iwate-Miyagi Nairiku earthquake (Mw6.8), Geophys. Res. Lett., 36, L20308, doi:10.1029/2009GL040063.
• Coseismic fault model of the 2008 Iwate-Miyagi Nairiku earthquake deduced by a dense GPS network

  Yusaku Ohta, Mako Ohzono, Satoshi Miura, Takeshi Iinuma, Kenji Tachibana, Kota Takatsuka, Kayo Miyao, Toshiya Sato, Norihito Umino

  EARTH PLANETS AND SPACE 60 (12) 1197 - 1201 1880-5981 2008 [Refereed][Not invited]
   

  A large earthquake of M-j 7.2 occurred on June 14, 2008, beneath the border between Iwate and Miyagi pre-fectures in northeastern Japan. We propose a simple rectangular fault model based on a dense GPS network, including continuous GPS sites run by four agencies, to describe the coseismic deformation. The coseismic displacements are estimated by kinematic PPP (precise point positioning) analysis. Near the hypocenter, co-located independent instruments (integrated accelerogram and kinematic PPP) measure the same large displacement caused by the mainshock. The fault model explains the observations well and reproduces the observed complex spatial pattern, especially around the northern part of the focal area, which is the focus of a debate on whether or not the coseismic slip occurred on the Dedana fault system. Our results show that no major slip on the Dedana fault system occurred. The estimated amount of moment release wits equivalent to M-w, 6.9, and the maximum slip reached 3.5 m on the southern sub-fault.
• Dense GPS array observations across the Atotsugawa fault system

  Hirahara, K, M. Ohzono, T. Sagiya, Y. Hoso, Y. Wada, M. Ando

  Geodynamics of Atotsugawa Fault System (Edited by M. Ando) 25 - 44 2007 [Refereed][Not invited]
  
• Crustal movement of antarctica and syowa station based on GPS measurements

  Mako Ohzono, Takao Tabei, Koichiro Doi, Kazuo Shibuya, Takeshi Sagiya

  EARTH PLANETS AND SPACE 58 (7) 795 - 804 1343-8832 2006 [Refereed][Not invited]
   

  In Antarctica, sea level rise and crustal uplift have occurred due to ice sheet melting and mantle response since the Last Glacial Maximum (LGM). The International GNSS Service (IGS) provides continuous data at nine sites on the Antarctic plate, and we analyzed data obtained from these sites between 1998 and 2003. Additional data were acquired by campaign observations around Syowa Station carried out by the Japanese Antarctic Research Expedition (JARE). Five sites around Syowa Station have been repeatedly occupied since 1098. Our analysis of the IGS data demonstrates that the Antarctic continent behaves as a rigid plate. Vertical components indicate an uplift of about 1.3-7.0 mm/year at almost all sites, which are attributed to the postglacial rebound. However, some observed velocities disagree with the predictions of glacial isostatic adjustment (GIA) models. It will be necessary to incorporate our results into the modeling of ice sheet melting. Around Syowa Station, the campaign GPS result is basically consistent with the IGS data analysis, thereby demonstrating that GPS observations properly represent the ongoing crustal movement around Syowa Station. However, the GPS results show some disagreement with the VLBI observations; this discrepancy will need to be sorted out using local tie observations that should be carried out in the near future.
• 2004年新潟県中越地震の震源域南部周辺における余効変動

  鷺谷威, 大園真子, 西脇周平, 太田雄策, 佐々木雅子, 山室友生, 木股文昭

  地震2 58 359 - 369 2005 [Refereed][Not invited]
  

MISC

• Supercritical geothermal system in the Niseko area, Shiribeshi region, southwestern Hokkaido

  田村慎, 岡大輔, 岡崎紀俊, 鈴木浩一, 中川光弘, 橋本武志, 高橋浩晃, 大園真子, 一柳昌義, 茂木透  日本地熱学会学術講演会講演要旨集  2021-  2021
• 平成30年北海道胆振東部地震とその災害に関する総合調査

  高橋 浩晃, 勝俣 啓, 大園 真子, 橋本 武志, 青山 裕, 酒井 慎一, 松本 聡, 岡田 知己, 小菅 正裕, 寺川 寿子, 飯尾 能久, 中尾 茂, 上嶋 誠, 柴田 智郎, 大津 直, 高井 伸雄, 飯場 正紀, 渡部 要一, 菊地 優, 岡崎 太一郎, 白井 和貴, 西村 裕一, 石川 達也, 高瀬 裕也, 永井 宏, 宮森 保紀, 三宅 弘恵, 松島 信一, 浅野 公之, 重藤 迪子, 卜部 厚志, 前田 宜浩, 石澤 友浩, 廣瀬 亘, 小山内 信智, 山田 孝, 笠井 美青, 檜垣 大助, 風間 基樹, 千木良 雅弘, 渦岡 良介, 竹林 洋史, 木村 誇, 石丸 聡, 岡田 成幸, 内田 賢悦, 有村 幹治, 植松 武是, 多々納 裕一, 梶谷 義雄, 能島 暢呂, 田村 圭子, 中村 洋光, 戸松 誠  自然災害科学総合シンポジウム講演論文集  56-  (56)  21  -26  2019/09/11  [Not refereed][Not invited]
   

  2019年9月11日(水), 於 : キャンパスプラザ京都 第1講義室「平成30年北海道胆振東部地震」とその災害に関する総合調査を実施した。震度７を記録した揺れにより, 同時多発斜面災害と, 北海道全域同時停電(ブラックアウト)が発生し, 複合的な災害となった。震源の深さは約37kmで, 大すべり域はそれより浅い20-25km付近であった。木造家屋の倒壊が多発したむかわ町市街では, 地盤構造による地震波の増幅が見られた。同時多発斜面崩壊は, 近隣の活火山の噴火による降下火砕堆積物が素因となった。札幌市内の地盤液状化地帯では, 極めて軟弱な谷埋盛土層が確認された。地震発生が未明であったことが, 建物倒壊による直接死が出なかったことに関係している可能性がある。ブラックアウトは, 社会経済活動に大きな影響を与えた。
• ニセコ山系東部における地熱構造モデリング

  岡大輔, 田村慎, 鈴木隆広, 大森一人, 岡崎紀俊, 高橋浩晃, 大園真子, 茂木透  日本地熱学会学術講演会講演要旨集  2019-  2019
• 北海道胆振地方の地震波速度構造

  椎名高裕, 勝俣啓, 一柳昌義, 高橋浩晃, 中村亮一, 加藤愛太郎, 大園真子, 青山裕, 田中良, 高田真秀, 山口照寛, 岡田和見, 酒井慎一, 松本聡, 岡田知己, 松澤暢, 平野舟一郎, 寺川寿子, 堀川信一郎, 小菅正裕, 片尾浩, 飯尾能久, 長岡愛理, 津村紀子, 上野友岳  日本地震学会秋季大会講演予稿集(CD-ROM)  2019-  2019
• 2018年北海道胆振東部地震の余震の震源メカニズム解と応力場

  薄田悠樹, 勝俣啓, 一柳昌義, 大園真子, 青山裕, 田中良, 高田真秀, 山口照寛, 岡田和見, 高橋浩晃, 酒井慎一, 松本聡, 岡田知己, 松澤暢, 平野舟一郎, 寺川寿子, 堀川信一郎, 小菅正弘, 片尾浩, 飯尾能久, 長岡愛理, 津村紀子, 上野友岳  日本地震学会秋季大会講演予稿集(CD-ROM)  2019-  2019
• Post‐seismic deformation of 2016 Kumamoto Earthquake by continuous GNSS network (3)

  NAKAO Shigeru, MATSUSHIMA Takeshi, TABEI Takao, OKUBO Makoto, YAMASHINA Tadashi, OHKURA Takahiro, NISHIMURA Takuya, NISHIMURA Takuya, SHIBUTANI Takuo, TERAISHI Masahiro, ITO Takeo, SAGIYA Takeshi, MATSUHIRO Kenjiro, KATO Teruyuki, FUKUDA Jun’ichi, WATANABE Atsushi, MIURA Satoshi, OHTA Yusaku, DEMACHI Tomotsugu, TAKAHASHI Hiroaki, OHZONO Mako, YAMAGUCHI Teruhiro, OKADA Kazumi  日本地球惑星科学連合大会予稿集(Web)  2019-  ROMBUNNO.SSS16‐P23 (WEB ONLY)  2019  [Not refereed][Not invited]
  
• 2016年熊本地震後のGNSSによる地殻変動観測(3)

  中尾茂, 松島健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本測地学会講演会要旨  130th-  173‐174  2018/10/16  [Not refereed][Not invited]
  
• ニセコ山系東部における地下構造推定のための精密重力探査

  岡大輔, 岡崎紀俊, 鈴木隆広, 高橋浩晃, 大園真子, 山口照寛  日本地熱学会学術講演会講演要旨集  2018-  2018
• Post‐seismic deformation of 2016 Kumamoto Earthquake by continuous GNSS network (2)

  NAKAO Shigeru, MATSUSHIMA Takeshi, TABEI Takao, OKUBO Makoto, YAMASHINA Tadashi, OHKURA Takahiro, NISHIMURA Takuya, SHIBUTANI Takuo, TERAISHI Masahiro, ITO Takeo, SAGIYA Takeshi, MATSUHIRO Kenjiro, KATO Teruyuki, FUKUDA Jun’ichi, WATANABE Atsushi, MIURA Satoshi, OHTA Yusaku, DEMACHI Tomotsugu, TAKAHASHI Hiroaki, OHZONO Mako, YAMAGUCHI Teruhiro, OKADA Kazumi  日本地球惑星科学連合大会予稿集(Web)  2018-  ROMBUNNO.SSS09‐P04 (WEB ONLY)  2018  [Not refereed][Not invited]
  
• 2016年熊本地震後のGNSSによる余効変動の観測(2)

  中尾茂, 松島健, 田部井隆雄, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本地震学会秋季大会講演予稿集(CD-ROM)  2017-  ROMBUNNO.S22‐14  2017/10/06  [Not refereed][Not invited]
  
• 2016年熊本地震後のGNSSによる地殻変動観測

  中尾茂, 松島健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本測地学会講演会要旨  128th-  153‐154  2017/10/04  [Not refereed][Not invited]
  
• Pre-state of stress on the fault of the 2016 Kumamoto earthquake (Mj7.3) inferred from moment tensor data of micro-earthquakes before the mainshock

  Satoshi Matsumoto, Yusuke Yamashita, Manami Nakamoto, Masahiro Miyazaki, Shin-ichi Sakai, Yoshihisa Iio, Kazuhiko Goto, Tomomi Okada, Mako Ohzono, Toshiko Terakawa, Masahiro Kosuga, Masayuki Yoshimi, Youichi Asano  EGU2017  2017-  2017/04  [Not refereed][Not invited]
  
• 2016年熊本地震後のGNSSによる地殻変動観測

  中尾茂, 松島健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本測地学会講演会要旨  126th-  141‐142  2016/10/19  [Not refereed][Not invited]
  
• カムチャツカ・クルチェフスコイ火山でのGNSS傾斜計観測

  高橋浩晃, 大園真子, 青山裕, 宮町宏樹, 松島健, 山下裕亮, GORDEEV E, MURAVYEV Y, SEROVETNIKOV S  日本測地学会講演会要旨  126th-  149‐150  2016/10/19  [Not refereed][Not invited]
  
• 2016年熊本地震後のGNSSによる余効変動の観測

  中尾茂, 松島健, 田部井隆雄, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本地震学会秋季大会講演予稿集  2016-  23  2016/09/16  [Not refereed][Not invited]
  
• カムチャッカ・クリュチェフスコイ火山での連続GNSS観測

  大園真子, 高橋浩晃, 青山裕, 宮町宏樹, 松島健, 山下裕亮, GORDEEV E, YAROSRAV M, SEROVETNIKOV S  日本火山学会講演予稿集  2016-  30  2016  [Not refereed][Not invited]
  
• GNSSによる2016年熊本地震発生後の地殻変動観測

  中尾茂, 松島健, 田部井隆雄, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見  日本地球惑星科学連合大会予稿集(Web)  2016-  ROMBUNNO.MIS34‐P31 (WEB ONLY)  2016  [Not refereed][Not invited]
  
• 蔵王山総合観測における地震観測網の展開

  平原聡, 三浦哲, 岡田知己, 中山貴史, 太田雄策, 立花憲司, 出町知嗣, 市來雅啓, 海田俊輝, 山本希, 西村太志, 大園真子  東京大学地震研究所技術研究報告  (20)  2015
• B1-05 Postseismic strain anomaly along Volcanic Front after the 2011 Tohoku Earthquake

  Miura Satoshi, Ohta Yusaku, Iinuma Takeshi, Demachi Tomotsugu, Tachibana Kenji, Sato Toshiya, Ohzono Mako  Programme and abstracts the Volcanological Society of Japan  2014-  59  -59  2014/11/02
• Detailed deformation associated with the 2011 off Pacific coast of Tohoku earthquake from a dense regional GPS network

  OHZONO M.  Japan Geoscience Union Meeting 2011, Chiba, Japan  2011
• 跡津川断層帯周辺の詳細地殻変動分布

  鷺谷威, 大園真子, 平原和朗, 橋本学, 竹内章, 細善信, 和田安男, 尾上健介, 大谷文夫, 道家涼介, 小澤和浩, 朝日友香  日本地震学会秋季大会講演予稿集  2009-  2009
• Coseismic fault model of the 2008 Iwate-Miyagi Nairiku earthquake deduced by a dense GPS network

  OHTA Yusaku, OHZONO Mako, MIURA Satoshi, IINUMA Takeshi, TACHIBANA Kenji, TAKATSUKA Kota, MIYAO Kayo, SATO Toshiya, UMINO Norihito  EPS  60-  (12)  1197  -1201  2008/12/01
• 2008年岩手・宮城内陸地震(M7.2)に伴った地震時・地震後地殻変動

  三浦哲, 太田雄策, 大園真子, 飯沼卓史, 立花憲司, 植木貞人, 高塚晃太, 宮尾佳世, 佐藤俊也, 対馬弘晃, 高橋浩晃, 山口照寛, 笠原稔, 鷺谷威, 小澤和浩, 福田真人, 朝日友香, 松島健, 中元真美, 山下裕亮, 中尾茂  日本地震学会秋季大会講演予稿集  2008-  5  2008/11/01  [Not refereed][Not invited]
  
• 2008年岩手・宮城内陸地震(M7.2)に伴った地震時・地震後地殻変動

  三浦哲, 太田雄策, 大園真子, 飯沼卓史, 立花憲司, 植木貞人, 高塚晃多, 宮尾佳世, 佐藤俊也, 対馬弘晃, 高橋浩晃, 山口照寛, 笠原稔, 鷺谷威, 小澤和浩, 福田真人, 朝日友香, 松島健, 中元真美, 山下裕亮, 中尾茂  日本地震学会ニュースレター  20-  (4)  10  -14  2008/10  [Not refereed][Not invited]
  
• 稠密GPS観測網による2008年岩手・宮城内陸地震の余効変動の時空間変化推定

  飯沼卓史, 大園真子, 太田雄策, 三浦哲, 植木貞人, 高塚晃多, 対馬弘晃, 立花憲司, 松島健, 中元真美, 山下裕亮, 鷺谷威, 小澤和浩, 福田真人, 朝日友香, 笠原稔, 高橋浩晃, 山口照寛, 中尾茂  日本測地学会講演会要旨  110th-  149  -150  2008/10  [Not refereed][Not invited]
  
• 跡津川断層系周辺における稠密GPS観測(2)

  大園真子, 鷺谷威, 橋本学, 細善信, 和田安男, 尾上謙介, 大谷文夫, 竹内章, 道家涼介, 平原和朗  日本地震学会秋季大会講演予稿集  2006-  2006

Presentations

• 2008年岩手宮城内陸地震における断層運動と粘性流動の相互作用および地震時すべり域と余効すべり域の重複  [Not invited]

  高田 陽一郎, 竹井 義貴, Moore James, Daniel Paul, 大園 真子

  JpGU2023  2023/05
• 北海道東部屈斜路カルデラ周辺の非定常地殻変動のモデル化  [Not invited]

  大園 真子, 高橋 浩晃, 山口 照寛

  JpGU2023  2023/05
• A Universal Feature of Postseismic Deformation Found in Inland and Megathrust Earthquakes  [Not invited]

  Meneses-Gutierrez, A, T. Sagiya, S. Miura, M. Ohzono

  AGU Fall Meeting 2022  2022/12
• 道東屈斜路カルデラ地域における精密重力モニタリング（2020年〜2021年）  [Not invited]

  名和一成, 山崎雅, 宮川歩夢, 高橋浩晃, 大園真子, 青山裕, 岡田和見, 山口照寛, 岡大輔, 岡崎紀俊, 今西祐一, 西山竜一, 本多亮, 池田博, 白川龍生, 大井拓磨

  日本測地学会第136回講演会  2021/11
• GNSS観測によるネパール・ヒマラヤ主要断層帯の固着推定  [Not invited]

  大園真子, 田部井隆雄, Bishow R. Silwal, Rajendra Bhandari, Janak B. Cahnd, Kandel Thakur, Soma N. Sapkota, 三宅弘恵, 纐纈一起

  日本測地学会第136回講演会  2021/11
• A universal feature of postseismic transient found in inland and interplate earthquakes

  Meneses-Gutierrez Angela, 鷺谷威, 三浦哲, 大園真子

  日本測地学会第136回講演会  2021/11
• 北西太平洋地域のプレート運動安定性の検討  [Not invited]

  石田優香, 高橋浩晃, 大園真子

  日本測地学会第136回講演会  2021/11
• 民間GNSS観測網を用いた地殻変動モニタリングの可能性  [Not invited]

  太田雄策, 大園真子

  日本測地学会第136回講演会  2021/11
• 稠密GNSS観測から見える北海道東部屈斜路カルデラ周辺の地殻ひずみ速度場 (2003-2020年)  [Not invited]

  大園真子, 高橋浩晃

  日本測地学会第136回講演会  2021/11
• 東北地方中南部における地震活動（序報）  [Not invited]

  岡田知己, 中山貴史, 平原聡, 堀内茂木, 勝俣啓, 大園真子, 小菅正裕, 前田拓人, 山中佳子, 片尾浩, 松島健, 八木原寛, 年東北地方太平洋沖地震緊急観測グループ

  日本地震学会2021年度秋季大会  2021/10
• 東北地方の応力場と発生した地震の断層面との関係（３）  [Not invited]

  田上綾香, 松野愛弥, 岡田知己, 酒井慎一, 大園真子, 勝俣啓, 小菅正裕, 山中佳子, 片尾浩, 松島健, 八木原寛, 中山貴史, 平原聡, 河野俊夫, 堀修一郎, 松澤暢, 年東北地方太平洋沖地震緊急観測グループ

  日本地震学会2021年度秋季大会  2021/10
• S波スプリッティング解析による東北地方の地震波速度異方性測定（４）  [Not invited]

  水田達也, 岡田知己, Savage Martha, 高木涼太, 吉田圭佑, 酒井慎一, 勝俣啓, 大園真子, 小菅正裕, 前田拓人, 山中佳子, 片尾浩, 松島健, 八木原寛, 中山貴史, 平原聡, 河野俊夫, 松澤暢, 年東北地方太平洋沖地震緊急観測グループ

  日本地震学会2021年度秋季大会  2021/10
• Physical modeling of postseismic deformation following the 2008 Iwate-Miyagi Nairiku Earthquake  [Not invited]

  Takei, Y, Y. Takada, J. D. P. Moore, M. Ohzono

  AGU 2020 Fall Meeting  2020/12
• 陸域GEONETによる北海道根室沖のプレート間固着推定の限界と新設GNSS-A観測点による推定範囲の検討  [Not invited]

  青田裕樹, 大園真子, 高橋浩晃, 太田雄策

  日本地震学会2020年度秋季学術大会  2020/10
• GNSS変位速度場から推定したネパール・ヒマラヤ主要断層帯の地震間プレートカップリング  [Not invited]

  田部井隆雄, 大園真子, Silwal Bishow, Bhandari Rajendra,Chand Janak, Sapkota Soma, 三宅弘恵, 纐纈一起

  日本地震学会2020年度秋季学術大会  2020/10
• 日本海東縁地域の応力場と発生した地震の断層面との関係(2)  [Not invited]

  田上綾香, 岡田知己, 酒井慎一, 大園真子, 勝俣啓, 小菅正裕, 山中佳子, 片尾浩, 松島健, 八木原寛, 中山貴史, 平原聡, 河野俊夫, 堀修一郎, 松澤暢, 2011年東北地方太平洋沖地震緊急観測グループ

  日本地震学会2020年度秋季学術大会  2020/10
• S波スプリッティング解析による東北地方の地震波速度異方性測定（２）  [Not invited]

  水田達也, 岡田知己, Savage Martha, 高木涼太, 吉田圭佑, 八木原寛, 松島健, 片尾浩, 山中佳子, 小菅正裕, 勝俣啓, 大園真子, 中山貴史, 平原聡, 河野俊夫, 松澤暢, 2011年東北地方太平洋沖地震緊急観測グループ

  日本地震学会2020年度秋季学術大会  2020/10
• 道東屈斜路カルデラ地域における精密重力モニタリング  [Not invited]

  名和一成, 山崎雅, 宮川歩夢, 山佳典史, 高橋浩晃, 大園真子, 岡田和見, 山口照寛, 岡大輔, 岡崎紀俊, 今西祐一, 西山竜一, 本多亮, 池田博, 白川龍生, 大井拓磨

  日本測地学会第134回講演会  2020/10
• 2008年岩手宮城内陸地震の余効変動における地殻内不均質構造の影響  [Not invited]

  竹井義貴, 高田陽一郎, James D.P. Moore, 大園真子

  日本測地学会第134回講演会  2020/10
• GNSS変位速度場から推定したネパール・ヒマラヤ主要断層帯の地震間カップリング  [Not invited]

  田部井隆雄, 大園真子, B. R. Silwal, R. Bhandari, J. B. Chand, S. N. Sapkota, 三宅弘恵, 纐纈一起

  日本測地学会第134回講演会  2020/10
• Measurement of seismic velocity anisotropy in the Tohoku region, NE Japan by shear wave splitting analysis

  Tatsuya Mizuta, Tomomi Okada, Martha K Savage, Ryota Takagi, Keisuke Yoshida, Hiroshi Yakiwara, Takeshi Matsushima, Hiroshi Katao, Yoshiko Yamanaka, Masahiro Kosuga, Kei Katsumata, Mako Ohzono, Takashi Nakayama, Satoshi Hirahara, Toshio Kono, Toru Matsuzawa, Group for the aftershock observations of th, off the Pacific coast, of, Tohoku Earthquake

  JpGU-AGU 2020 Joint Meeting
• Stress field in the eastern margin of the Japan Sea and its relationship with faults of recent earthquakes

  Ayaka Tagami, Tomomi Okada, Shin'ichi Sakai, Mako Ohzono, Kei Katsumata, Masahiro Kosuga, Yoshiko Yamanaka, Hiroshi Katao, Takeshi Matsushima, Hiroshi Yakiwara, Takashi Nakayama, Satoshi Hirahara, Toshio Kono, Shu'ichiro Hori, Toru Matsuzawa, Group for, the aftershock observations of th, off the Pacific coast, of, Tohoku Earthquake

  JpGU-AGU 2020 Joint Meeting
• Earthquake potential evaluation in the Himalayan Frontal Zone using space geodetic technique

  Tabei, T, M. Ohzono, B. R. Silwal, R. P. Bhandari, J. B. Chand, S. N. Sapkota, H. Miyake, K. Koketsu

  JpGU-AGU 2020 Joint Meeting
• Physical modeling of postseismic deformation following the 2008 Iwate-Miyagi Nairiku Earthquake  [Not invited]

  Takei, Y, Y. Takada, J. Moore, M. Ohzono

  JpGU-AGU 2020 Joint Meeting
• Convergence boundary between Amurian and Okhotsk plates in northernmost Japan and south Sakhalin inferred by GNSS velocity data  [Not invited]

  Ito, C, H. Takahashi, M. Ohzono, N. F. Vasikenko, A. S. Prytkov

  AGU Fall Meeting 2019  2019/12
• アジア大陸ー日本島弧を結ぶGNSS基線長変化の予備解析  [Not invited]

  大園真子, 高橋浩晃, Meng Guogie, Wu Weiwei

  日本測地学会第132回講演会  2019/10
• 人工地震探査による姶良カルデラ下の速度構造（4）  [Not invited]

  宮町宏樹, 小林励司, 八木原寛, 平野舟一郎, 久保武史, 早田正和, 坂尾健有, 海野直弘, 松島健, 内田和也, 宮町凛太郎, 磯田謙心, Agnis Triahadini, 手操佳子, 神谷義之介, 清水洋, 片尾浩, 澁谷拓郎, 三浦勉, 中川潤, 米田格, 加藤慎也, 為栗健, 瀧下恒星, 仲井一穂, 山下裕亮, 前田裕太, 渡辺俊樹, 堀川信一郎, 松廣健二郎, 奥田隆, 辻修平, 十川直樹, 長谷川大真, 中東和夫, 蔵下英司, 岩崎貴哉, 篠原雅尚, 山田知朗, 阿部英二, 安藤美和子, 田中伸一, 池澤賢志, 佐藤利典, 山本希, 平原聡, 中山貴史, 東龍介, 日野亮太, 大友周平, 鈴木秀市, 筒井智樹, 井上雄介, 竹井瑠一, 多田悠也, 高橋浩晃, 青山裕, 大園真子, 椎名高裕, 高田真秀, 一柳昌義, 山口照寛, 小野夏生, 齊藤一真, 伊藤ちひろ, 薄田悠樹, 村井芳夫, 中垣達也, 田中康久

  火山学会2019年度秋季大会  2019/09
• 北海道胆振地方の地震波速度構造  [Not invited]

  椎名高裕, 勝俣啓, 一柳昌義, 高橋浩晃, 中村亮一, 加藤愛太郎, 大園真子, 青山裕, 田中良, 高田真秀, 山口照寛, 岡田和見, 酒井慎一, 松本聡, 岡田知己, 松澤暢, 平野舟一郎, 寺川寿子, 堀川信一郎, 小菅正裕, 片尾浩, 飯尾能久, 長岡愛理, 津村紀子, 上野友岳, 年北海道胆振東部地震合同観測グループ

  日本地震学会2019年度秋季大会  2019/09
• 人工地震探査による南九州横断測線下の速度構造（4）  [Not invited]

  宮町宏樹, 小林励司, 八木原寛, 平野舟一郎, 久保武史, 海野直弘, 松島健, 内田和也, 宮町凜太郎, 片尾浩, 澁谷拓郎, 三浦勉, 中川潤, 米田格, 為栗健, 瀧下恒星, 仲井一穂, 山下裕亮, 前田裕太, 堀川信一郎, 松廣健二郎, 奥田隆, 辻修平, 十川直樹, 中東和夫, 蔵下英司, 山田知朗, 安藤美和子, 田中伸一, 池澤賢志, 佐藤利典, 山本希, 平原聡, 中山貴史, 東龍介, 鈴木秀市, 筒井智樹, 竹井瑠一, 多田悠也, 高橋浩晃, 青山裕, 大園真子, 椎名高裕, 髙田真秀, 一柳昌義, 山口照寛, 伊藤ちひろ, 薄田悠樹, 村井芳夫, 中垣達也

  日本地震学会2019年度秋季大会  2019/09
• 千島海溝南西部根室沖における海底測地観測網の構築  [Not invited]

  太田雄策, 木戸元之, 東龍介, 佐藤真樹子, 鈴木秀市, 山本龍典, 高橋秀暢, 木村友季保, 大塚英人, 本荘千枝, 日野亮太, 大園真子, 岡田和見, 青田裕樹, 高橋浩晃, 篠原雅尚, 富田史章, 金松敏也, ション カンシー, 飯沼卓史

  日本地震学会2019年度秋季大会  2019/09
• 2018年北海道胆振東部地震の余震の震源メカニズム解と応力場  [Not invited]

  薄田悠樹, 勝俣啓, 一柳昌義, 大園真子, 青山裕, 田中良, 高田真秀, 山口照寛, 岡田和見, 高橋浩晃, 酒井慎一, 松本聡, 岡田知己, 松澤暢, 平野舟一郎, 寺川寿子, 堀川信一郎, 小菅正弘, 片尾浩, 飯 尾能久, 長岡愛理, 津村紀子, 上野友岳, 年北海道胆振東部地震合同地震観測グループ

  日本地震学会2019年度秋季大会  2019/09
• 2016 年熊本地震後のGNSS による地殻変動観測（3）  [Not invited]

  中尾 茂, 松島 健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷 威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦 哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見

  日本測地学会第130回講演会  2018/10
• ネパールにおけるGNSS 観測網の整備と地震ポテン シャル評価：第2 報  [Not invited]

  田部井隆雄, 大園真子, 纐纈一起, 三宅弘恵, Rajendra Bhandari, Janak B. Ch, Bishow R. Silwal, Soma N. Sapkota

  日本測地学会第130回講演会  2018/10
• GNSSデータによる内陸SSEの検出  [Not invited]

  大園真子, 髙橋浩晃, 一柳昌義

  日本測地学会第130回講演会  2018/10
• GNSSデータに基づく石狩低地東縁断層帯周辺のひずみの時空間分布と地震活動によるその収支について  [Not invited]

  大園真子, 高橋浩晃, 伊藤ちひろ

  2018年日本地震学会秋季大会  2018/10
• 2018年北海道胆振北部地震の本震ー余震活動  [Not invited]

  勝俣啓, 大園真子, 青山裕, 田中良, 高田真秀, 一柳昌義, 山口照寛, 岡田和見, 高橋浩晃, 酒井慎一, 松本聡, 岡田知己, 中尾茂, 寺川寿子, 小菅正裕, 飯尾能久, 年胆振東部地震合同地震観測グループ

  2018年地震学会秋季大会  2018/10
• 粘弾性火山変動における弾性層厚不均一性の兆候  [Not invited]

  山崎雅, 高橋浩晃, 大園真子, Tim J. Wrigh, 小林知勝

  日本火山学会2018年秋季大会  2018/09
• 2016 年熊本地震後の粘弾性緩和と阿蘇カルデラ周辺 の地下構造との関係  [Not invited]

  不破智志, 大園真子

  日本火山学会2018年秋季大会  2018/09
• Convergence velocity between Amurian plate and north American plate estimated by GNSS at northern part of Hokkaido, Japan  [Not invited]

  Ito, C, N. Vasilenko, A. Prytkov, H. Takahashi, M. Ohzono

  4th ICCE  2018/05
• Impact on continental deformation field in NE Asia due to subduction great earthquakes  [Not invited]

  Takahashi, H, M. Ohzono, C. Ito, N.V. Shestakov, M.D. Gerasimenko

  4th ICCE  2018/05
• The effect of large postseismic relaxation around northeast Asia  [Not invited]

  Ohzono, M, H. Takahashi, N.V. Shestakov, G. Meng, M.D. Gerasimenko

  4thICCE  2018/05
• Viscosity distribution beneath the Kyushu Island estimated by GNSS postseismic time sereis of the 2016 Kumamoto earthquake (M7.3)  [Not invited]

  Fuwa, S, M. Ohzono

  4th ICCE  2018/05
• Dynamic strain and induced earthquakes due to the 2016 Kumamoto earthquake (Mw7.0), Kyushu, Japan  [Not invited]

  Saito, K, H. Takahashi, M. Ohzono

  4th ICCE  2018/05
• ossibility of the real-time dynamic strain field monitoring deduced from GNSS data: case study of the 2016 Kumamoto earthquake sequence  [Not invited]

  Ohta, Y, M. Ohzono, H. Takahashi, S. Kawamoto, R. Hino

  AGU 2017 Fall Meeting  2017/12
• Estimation of the long-term effect of viscoelastic relaxation induced by the 2011 Tohoku earthquake and other interplate earthquakes around northeastern Asia  [Not invited]

  Ohzono, M, H. Takahashi, N. Shestakov, G. Meng, M. Gerasimenko

  AGU 2017 Fall Meeting  2017/12
• 2016年熊本地震後GNSS観測による余効変動の観測(2)  [Not invited]

  中尾茂, 松島健, 田部井隆雄, 山科匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見

  日本地震学会2017年秋季大会  2017/10
• 屈斜路カルデラ周辺の温度構造とひずみ分布  [Not invited]

  高橋浩晃, 大園真子, 一柳昌義, 岡崎紀俊, 鈴木隆広, 秋田藤夫

  日本地震学会2017年秋季大会  2017/10
• ネパールにおけるGNSS観測網の整備と地震ポテンシャル評価:序報  [Not invited]

  田部井隆雄, 大園真子, 纐纈一起, 三宅弘恵, R. Bhandari, J. B. Chand, S. N. Sapkota

  日本地震学会2017年秋季大会  2017/10
• 2011年東北地方太平洋沖地震(M9.0)による北東アジア地域の余効変動とレオロジー構造の推定  [Not invited]

  大園真子, 高橋浩晃, N. V. Shestacov, G. Meng, M. D. Gerasimenko

  日本地震学会2017年秋季大会  2017/10
• 屈斜路カルデラ周辺の地温勾配分布  [Not invited]

  高橋浩晃, 大園真子, 岡崎紀俊, 鈴木隆広, 秋田藤夫

  日本火山学会2017年度秋季大会  2017/09
• Post-seismic deformation of 2016 Kumamoto Earthquake by continuous GNSS network  [Not invited]

  中尾茂, 松島健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見

  JpGU-AGU Joint Meeting 2017  2017/05
• GNSSデータを用いた日本海東縁周辺の地震間地殻変動場の時空間変化  [Not invited]

  佐藤未佳, 大園真子, 長谷見晶子

  JpGU-AGU Joint Meeting 2017  2017/05
• Pre-state of stress on the fault of the 2016 Kumamoto earthquake (Mj7.3) inferred from moment tensor data of micro-earthquakes before the mainshock  [Not invited]

  Matsumoto, S, Y. Yamashita, M. Nakamoto, M. Miyazaki, S. Sakai, Y. Iio, K. Goto, T. Okada, M. Ohzono, T. Terakawa, M. Kosuga, M. Yoshimi, Y. Asano

  EGU2017  2017/04
• Transient responses of surface properties to large earthquakes: what do we learn from coupling geomorphological and geophysical data?  [Not invited]

  Hovius, N, O. Marc, C. Sens-Schönfelder, P. Meunier, L. Illien, M. Hobiger, Y. Hsu, M. Ohzono, K. Sawazaki, C. Rault

  EGU2017  2017/04
• 2016年熊本地震後のGNSSによる地殻変動観測  [Not invited]

  中尾茂, 松島健, 田部井隆雄, 大久保慎人, 山品匡史, 大倉敬宏, 西村卓也, 澁谷拓郎, 寺石眞弘, 伊藤武男, 鷺谷威, 松廣健二郎, 加藤照之, 福田淳一, 渡邉篤志, 三浦哲, 太田雄策, 出町知嗣, 高橋浩晃, 大園真子, 山口照寛, 岡田和見

  日本測地学会第126回講演会  2016/10
• カムチャツカ・クルチェフスコイ火山でのGNSS傾斜計観測  [Not invited]

  高橋浩晃, 大園真子, 青山裕, 宮町宏樹, 松島健, 山下裕亮, E.ゴルディエフ, Y.ムラビヨフ, S.セロベトニコフ

  日本測地学会第126回講演会  2016/10
• GNSSデータに基づく2016年熊本地震の前震・本震時のひずみ・応力変化  [Not invited]

  大園真子, 高橋浩晃

  日本測地学会第126回講演会  2016/10
• カムチャッカ・クリュチェフスコイ火山での連続 GNSS観測  [Not invited]

  大園真子, 高橋浩晃, 青山裕, 宮町宏樹, 松島健, 山下裕亮, ゴルディエフ E, ヤロスラフ M, セロベトニコフ S

  日本火山学会2016年秋季大会  2016/10
• 北東アジア地域における日本周辺の大地震に伴う長期余効変動の影響の推定  [Not invited]

  大園真子, 高橋浩晃, N. V. シェスタコフ, 孟国杰, M. D. ゲラシメンコ

  日本地震学会2016年秋季大会  2016/10
• Plate convergence, slow slip, and seismic activity along eastern margin of Amurian plate  [Not invited]

  Takahashi, H, M. Ohzono, N. Shestakov, A. Prytkov, N. Vasilenko

  AOGS2016  2016/08
• Observation and modeling of the far-field postseismic displacements caused by the great 2011 Tohoku earthquake  [Not invited]

  Shestakov, N, G. Meng, W. Wu, M. Gerasimenko, M. Ohzono, H. Takahashi

  AOGS2016  2016/08
• Have the postseismic motions due to the may 24, 2013 Mw8.3 Okhotsk deep focus earthquake been discovered by the Russian far east GNSS networks?  [Not invited]

  Shestakov, N, G. Nechaev, N. Titkov, M. Gerasimenko, V. Bykov, V. Pupatenko, S. Serovetnikov, A. Prytkov, N. Vasilenko, D. Sysoev, A. Sorokin, H. Takahashi, M. Ohzono

  JKASP2016  2016/06
• Magma, thermal structure, strain concentration and active seismicity in Kussharo caldera, Hokkaido  [Not invited]

  Takahashi, H, M. Ohzono, K. Minato, N. Okazaki, T. Suzuki, T. Takahashi, F. Akita

  JKASP2016  2016/05
• Estimation of the long-term effect of viscoelastic relaxation induced by the 2011 Tohoku earthquake and other interplate earthquakes around northeastern Asia  [Not invited]

  Ohzono, M, H. Takahashi, N. V. Shestakov, G. Meng, M.D. Gerasimenko

  JKASP2016  2016/05
• GEONETのGPS座標値と傾斜計記録による2015年6月4日の阿寒湖付近の地震時地殻変動の検討  [Not invited]

  大園真子, 高橋浩晃, 一柳昌義

  日本測地学会第124回講演会  2015/10
• 地震間の定常的なひずみは2011年東北地方太平洋沖地震でどれだけ解放されたのか？  [Not invited]

  大園真子, 長谷見晶子

  JpGU2015年大会  2015/05
• 2012年北海道北部の群発地震に誘発された内陸スロースリップイベント？  [Not invited]

  大園真子, 高橋浩晃, 一柳昌義, 東龍介, 山口照寛, 山田卓司, 谷岡勇市郎

  JpGU2013年大会  2013/05
• 2011年東北地方太平洋沖地震に伴う東北日本の地殻不均質に起因するひずみ異常分布, JpGU2012年大会  [Invited]

  大園真子, 矢部康男, 飯沼卓史, 太田雄策, 三浦哲, 立花憲司, 佐藤俊也, 出町知嗣

  JpGU2012年大会  2012/05
• GPS観測による2008年岩手・宮城内陸地震の長期的余効変動  [Not invited]

  大園真子, 三浦哲, 太田雄策, 飯沼卓史

  日本地震学会2010年秋季大会  2010/10
• 2008年岩手・宮城内陸地震に伴う余効変動から推定された震源域周辺の粘弾性構造  [Not invited]

  大園真子, 三浦哲, 太田雄策, 飯沼卓史, 立花憲司, 佐藤俊也, 出町知嗣

  JpGU2010年大会  2010/05
• ブロック回転・すべり欠損モデルに基づく2008年岩手・宮城内陸地震に伴った地殻変動の時間依存インバージョン  [Not invited]

  大園真子, Robert McCaffrey, 太田雄策, 三浦哲, 飯沼卓史, 立花憲司, 佐藤俊也

  日本測地学会第112回講演会  2009/10
• 稠密GPS観測に基づく出店断層周辺におけるひずみ蓄積過程 -2008年岩手・宮城内陸地震前後の時空間変化-  [Not invited]

  大園真子, 三浦哲, 太田雄策, 飯沼卓史, 立花憲司, 佐藤俊也, 植木貞人, 対馬弘晃, 宮尾佳世, 高塚晃多

  日本測地学会第110回講演会  2008/10
• GPS観測に基づく跡津川断層系周辺の地殻変動のモデル化: ひずみ集中帯の変形様式と断層走向方向の不均質性  [Not invited]

  大園真子, 平原和朗, 鷺谷威, 細善信, 和田安男, 安藤雅孝

  地球惑星科学関連学会2006年合同大会  2006/06
• GPS観測に基づく跡津川断層系周辺の地殻変動 -二測線の比較から見る断層走向方向の不均質性-  [Not invited]

  大園真子, 平原和朗, 細喜信, 和田安男, 鷺谷威, 安藤雅孝

  日本地震学会2005年秋季大会  2005/10
• GPS観測に基づく南極大陸の地殻変動  [Not invited]

  大園真子, 田部井隆雄, 土井浩一郎, 渋谷和雄

  地球惑星科学関連学会2005年合同大会  2005/05
• GPS観測による南極昭和基地周辺のPost-Glacial Reboundの検出  [Not invited]

  大園真子, 田部井隆雄, 土井浩一郎, 青木茂, 岩野祥子, 吉井弘治, 福崎順洋, 小澤拓

  地球惑星科学関連学会2004年合同大会  2004/05

Teaching Experience

Applied Metrology to Seismology and VolcanologyApplied Metrology to Seismology and Volcanology Hokkaido University

Association Memberships

• American Geophysical Union   JAPAN GEOSCIENCE UNION   THE SEISMOLOGICAL SOCIETY OF JAPAN   The Geodetic Society of Japan   

Research Projects

• Explore the slow earthquake in Kamchatka subduction zone

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2020/10 -2024/03 

  Author : 高橋 浩晃, 宮町 宏樹, 松島 健, 山下 裕亮, 大園 真子

   

  昨年度に選定した傾斜計・広帯域地震計及び周辺機器が納入され試験観測を実施し性能確認を行った。観測システムは200V入力仕様で停電及び雷対策のためにトランスと充電器から機器に給電する方式とし、停電時でも１カ月程度はオペレーションが可能な電力容量を予定した。データロガーは広帯域地震計からのアナログ入力と傾斜計からのシリアル入力を同時に可能とするファームウエアを新たに開発した。観測点の選定をロシア側研究機関と進め、電力やインターネット、セキュリティの関係から、ペトロパブロフスクの海岸付近にある灯台敷地内と、約10km程度海岸から離れた地震観測所とした。傾斜計を設置するボアホール井戸の設計を実施し、掘削孔は10m程度の深度のポリ塩化ビニルケーシング100mmの密閉型完全防水とし、ケーシングの傾斜2度以内、ローラーコーンビットによる掘削を行った後、ケーシング周辺をセメントで充填する仕様書を作成した。ロシア側研究機関が選定した業者との仕様打ち合わせ及び工事価格調整を行い、見積書の発行を受け、随意契約による国際発注の手続きを進めた。また、観測機器の輸出手続きに必要な非該当証明等の手続きも進めた。2022年2月にロシアがウクライナに侵攻した関係で、外務省からロシアへ渡航中止勧告が出され、経済産業省から外国為替及び外国貿易法に基づきロシアへの輸出が役務取引を含め原則承認されないこととなったため、傾斜計用ボアホールの役務発注及び機器輸出の準備を中断した。今後の研究の進め方については、国の規制の動向を見つつ、既存データの利用等を含めた検討を行うこととした。
• 超稠密GNSS観測による地球科学への応用研究

  東京大学地震研究所：共同利用特定共同研究（B）

  Date (from‐to) : 2023/04 -2024/03
• Precise gravity monitoring in and around the Kussharo Caldera at eastern Hokkaido, Japan

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 名和 一成, 大園 真子, 今西 祐一, 本多 亮, 岡 大輔, 白川 龍生

   

  本研究は、火山や地震など地殻活動域である道東カルデラ火山地域の重力場を、長期間、高時空間分解能で把握することを目的としている。屈斜路カルデラ周辺を対象フィールドとし、長期に安定で連続観測可能な超伝導重力計と、ドリフトフリーな絶対重力計、可搬型で連続測定も容易なスプリング式相対重力計を効果的に組み合わせて使用し、地下のマグマ活動や断層運動、それらに関係する物性変化や地表変形に伴う重力変化の検出を目指す。地下からの重力シグナルは微弱なため、それとレベルの重力変化を生じうる環境擾乱を高精度に把握し分離することも課題である。 2018年11月に弟子屈観測所においてiGrav型超伝導重力計(#017)による連続観測を開始して以降、毎年冷凍機交換等の保守作業を行い、順調に観測を継続している。超伝導重力計のスケールファクターとドリフト検定を目的として絶対重力計FG5(#241)と並行観測を2019年、2020年に引き続き実施した。多点同時観測用にスプリング式のgPhone重力計を新たに導入した。gPhone重力計は仁伏で一時的に連続測定を行った後、積雪期前に弟子屈観測所に移設し、超伝導重力計との並行観測を開始した。導入済みのCG5, ED型重力計については、それぞれ仁伏と屈斜路点で冬季の連続測定を実施した。重力観測への影響を定量化するために、前シーズンに引き続き、簡易積雪重量計およびタイムラプスカメラによる積雪観測を継続した。屈斜路湖の北端と南端に水位（水圧）計を設置し、連続測定を開始した。さらに、地面振動やセイシュに与える気圧変化の影響を調べるため、仁伏と弟子屈において、高精度微気圧計による連続観測を開始した。
• 中国ロシア日本を統合するGNSS観測ネットワークで見る東アジア変動帯の全容

  日本学術振興会：科研費基盤研究（B）

  Date (from‐to) : 2019/04 -2023/03 

  Author : 高橋 浩晃
• 平成30年北海道胆振東部地震とその災害に関する総合調査

  日本学術振興会：科研費・特別研究推進費

  Date (from‐to) : 2018/10 -2019/03 

  Author : 高橋 浩晃
• 群発地震に伴う内陸スロー地震の検出

  日本学術振興会：科学研究費・新学術・公募

  Date (from‐to) : 2017/04 -2019/03 

  Author : 大園 真子
• 島弧地殻における変形・断層すべり過程のモデル構築

  日本学術振興会：科研費・新学術・研究計画

  Date (from‐to) : 2014/04 -2019/03 

  Author : 芝崎 文一郎
• 地球物理学的観測によるアジア北東地域のテクトニクスモデルの刷新

  日本学術振興会：科研費・基盤A

  Date (from‐to) : 2013/04 -2018/03 

  Author : 高橋 浩晃
• 東北沖地震後の地殻変動を予測する岩石の遷移挙動レオロジーの実験的研究

  日本学術振興会：科研費・基盤B

  Date (from‐to) : 2014/04 -2017/03 

  Author : 武藤 潤
• 測地学的データに基づく東北地方の内陸活断層周辺におけるひずみ蓄積過程の解明

  日本学術振興会：科研費・特別研究員

  Date (from‐to) : 2008/10 -2011/03 

  Author : 大園 真子

   

  本年度は,2008年岩手・宮城内陸地震後に観測した長期・広域の余効変動を説明するための粘弾性構造モデルの構築を試みた.また,先行研究との比較,モデルで説明できない部分についての考察を行い,博士論文としてまとめた.2010年8月31日までの稠密GPS観測から,水平成分で太平洋側から日本海側に至る広い範囲で10mm以上の変位が,上下成分で震源域近傍の顕著な沈降が見られた.この余効変動の主要因が粘弾性緩和であると判断し,粘弾性構造モデルによる推定を行った.上部地殻に対応する弾性層と下部地殻以深の粘弾性層から成る球殻成層構造を仮定し,弾性層の厚さHおよび粘弾性層の粘性係数ηの最適値を探索した.震源域近傍は他の要因による影響の可能性が考えられたため,試行錯誤の末,震央距離35km以上に分布する観測点のみを推定に用いた.2期間について調べた結果,本震後2ヶ月-1.5年間の観測値は,H=19.5-25.5km,η=2.4-3.4E+18Pa・s,2ヶ月-2.2年間の観測値は,H=17.0-23.5km,η=3.1-4.8E+18Pa・sとした時に最も良く説明される.推定した弾性層の下端の深さは,本研究対象領域の地震発生領域の下端に概ね対応している.粘性係数は,1896年陸羽地震後の余効変動から推定された結果の約1/3となる.この違いは,奥羽脊梁山脈直下の局所的低粘性領域を反映していることや,定常状態に戻る前の時間変化を見ていることなどの可能性が考えられるが本研究では結論づけられない.粘弾性緩和モデルのみでは説明できない残差が震源域近傍で生じるが,震源断層直上の2点については,この残差の約7-8割が余効すべりで説明でき,先行研究の推定とも概ね一致する.今後は,他の測地観測データと共に,地震波低速度域や火山の存在を考慮した,水平方向にも不均質な粘弾性構造モデルによる推定が重要となる.