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Master

Affiliation (Master)

  • Faculty of Engineering　Division of Architecture　Research Group of Structural Engineering and Materials

Affiliation (Master)

  • Faculty of Engineering　Division of Architecture　Research Group of Structural Engineering and Materials

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Profile and Settings

Profile and Settings

  • Name (Japanese)

    Takai

  • Name (Kana)

    Nobuo

  • Name

    D-6141-2012, 200901029820571238

Achievement

Research Interests

  • 強震動   地盤震動   都市防災   地震工学   Earthquake Eng.   

Research Areas

  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Structural and seismic engineering
  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Disaster prevention engineering
  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Building structures and materials

Research Experience

  • 2005 - Today - 北海道大学大学院工学研究科 助教授
  • 2005 - Today - Associate Professor
  • 1996 - 2005 北海道大学助手（工学部建築工学科耐震工学講座) 助手
  • 1996 - 2005 Assistant Professor
  • 1996/04 - 1996/05 日本学術振興会特別研究員 日本学術振興会特別研究員
  • 1996/04 - 1996/05 Postdoctoral Fellowships of Japan Society for the Promotion of Science

Education

  • 1995/04 - 1996/05  Hokkaido University  Graduate School of Engineering  Division of Architecture Engineering Doctor Course
  • 1993/04 - 1995/03  Hokkaido University  Graduate School of Engineering  Division of Architecture Engineering
  • 1989/04 - 1993/03  Hokkaido University  Faculty of Engineering  School of Architecture Engineering

Published Papers

  • Roshan Prajapati, Salim Dhonju, Subeg Man Bijukchhen, Michiko Shigefuji, Nobuo Takai
    Earth, Planets and Space 76 (1) 2024/10/25 [Refereed]
     
    Abstract The severe damage observed in the Kathmandu Basin, Nepal, during past earthquakes necessitates a thorough study of the seismic behavior of the basin sediments. As the shear-wave velocity is directly related to the elastic shear modulus of the material, it is essential to determine it to incorporate the behavior of the soil in the design of the structure. Hence, we determined average shear-wave velocity in upper 30 m (Vs30) of soil in Bhaktapur district in the eastern part of the Kathmandu Basin at 73 observation points, employing two methods involving the use of non-invasive microtremor array measurements (MAMs). These MAMs are widely used for determining subsurface soil characteristics by analyzing the ambient vibrations of the ground. The first method involves inversion using a genetic algorithm, and the second is a method for obtaining Vs30 directly from the dispersion curve. We found that Vs30 in the southeastern part of the study area was higher than that in other parts. Conversely, Vs30 in the western region was lower. The calculated Vs30 values were used to classify the sites. The elevated eastern and southeastern areas with high Vs30 were categorized as dense soil or soft rock, whereas the areas with low Vs30 that had suffered significant damage during the 2015 Gorkha earthquake were classified as soft soil sites. Graphical Abstract
  • Michiko Shigefuji, Nobuo Takai, Subeg Man Bijukchhen, Chintan Timsina, Mukunda Bhattarai
    Earth, Planets and Space 76 (1) 2024/05/13 [Refereed]
     
    Abstract The Himalayan collision zone, where the Indian Plate subducts beneath the Eurasian Plate at a low angle, has caused many devastating earthquakes. The Kathmandu basin, situated in this region, is surrounded by mountains on all sides and is filled with distinct soft lake sediments with a highly undulating bedrock topography. The basin has been experiencing rapid urbanization, and the growing population in its major cities has increased the vulnerability to seismic risk during future earthquakes. Several strong-motion stations have recently been deployed in the Kathmandu basin. It is expected that the data captured by this strong-motion station array will further enhance our understanding of site amplification in sedimentary basins. Clear P-to-S converted waves have been observed in the strong-motion records. In this study, we investigate the medium boundary that generated these converted waves. First, we estimate the shallow velocity structures, which correspond to the topographic slopes or surface geology, beneath the strong-motion stations. We then apply a receiver function analysis to the strong-motion records. The receiver function indicates that the interface between the soft sediment and seismic bedrock serves as a boundary that generates converted waves. The obtained results can be used for tuning three-dimensional velocity structures. Graphical Abstract
  • Nakagawa N, Takai N, Shigefuji M
    Earth, Planets and Space 75 (1) 42  2023/03 [Refereed]
     
    The Yufutsu Plain, a sedimentary basin surrounded by mountains, is located in the southern part of the Ishikari-Yufutsu Lowlands, Hokkaido, Japan. The Hidaka arc-arc collision zone, located in the eastern part of the Yufutsu Plain, forms the Hidaka Mountain range in central Hokkaido, with the Ishikari-Teichi-Toen Fault Zone of the Ishikari-Yufutsu Lowlands on the west side, which forms part of a major geological boundary that extends in the north-south direction. The 2018 Hokkaido Eastern Iburi earthquake (M-w 6.6) occurred at 03:08 JST on September 6, 2018, in this arc-arc collision zone. The K-NET HKD126 station in Mukawa Town, which is close to the severely damaged basin margin area, recorded strong-motion data with strong power for a predominant frequency of 0.5-1.0 Hz during the main shock. The peak ground acceleration was 661 cm/s(2) in the east-west direction. The site amplification characteristics of the shallow S-wave velocity structure, which was estimated from microtremor array observations and surface wave explorations, were one of the causes of this strong ground motion. It is essential to accurately estimate the depth of the seismic bedrock and basin margin to evaluate the long period of large earthquakes. In this study, we used strong-motion data recorded at HKD126 and three temporary strong-motion stations near the basin margin area to tune the deep S-wave velocity structure. First, we performed microtremor array observations and surface wave explorations to estimate the S-wave velocity structure to a depth of 1 km beneath the station at the hill site because a detailed shallow structure is not available for this site. Then, with a combination of the estimated S-wave velocity structure and the existing structure, we tuned the deep structures based on an autocorrelation function analysis using strong-motion data. The validity of the estimated structures from the shallowest depth to the seismic bedrock was verified based on the differences between the observed arrival time difference and theoretical travel time difference for the S-wave initial motion. We estimated the seismic bedrock of the four stations to be at a depth of 7-10 km. In addition, an autocorrelation function analysis suggests topological bedrock undulations.
  • Nobuo Takai, Naofumi Nakagawa, Michiko Shigefuji, Shingo Nomoto, Tetsunori Kishikawa, Jun Horita, Shunzo Kawajiri, Seiji Tsuno, Hiroaki Yamanaka
    BUTSURI-TANSA(Geophysical Exploration) 75 98 - 104 0912-7984 2022/12 [Refereed][Not invited]
  • Michiko Shigefuji, Nobuo Takai, Subeg Bijukchhen, Masayoshi Ichiyanagi, Sudhir Rajaure, Megh Raj Dhital, Lalu Prasad Paudel, Tsutomu Sasatani
    Scientific Data 9 (1) 2052-4463 2022/08/20 [Refereed]
     
    Abstract Strong-motion records of earthquakes are used not only to evaluate the source rupture process, seismic wave propagation and strong ground motion characteristics, but also to provide valuable data for earthquake disaster mitigation. The Kathmandu Valley, Nepal, which is characterised by having soft sediments that have been deposited in an earthquake-prone zone, has experienced numerous earthquakes. We have operated four strong-motion stations in the Kathmandu Valley since 2011. These stations recorded the 2015 magnitude 7.8 Gorkha Nepal earthquake that occurred in the Himalayan continental collision zone. For several months after the mainshock, we deployed four additional temporary stations. Here, we describe the seismic data for 18 earthquakes over magnitude 5.0 collected by this array, including the 2015 magnitude 7.3 Dolakha earthquake of maximum aftershock and three large aftershocks of magnitude 6-class. These data are essential for validating the sedimentary structure of the basin and for evaluating the hazard and risk of future earthquakes in the Kathmandu Valley.
  • Seiji Tsuno, Hiroaki Yamanaka, Shunzo Kawajiri, Akinobu Ogasawara, Nobuo Takai, Naofumi Nakagawa, Michiko Shigefuji, Shingo Nomoto, Tetsuhiro Kishikawa, Jun Horita
    BUTSURI-TANSA(Geophysical Exploration) 75 56 - 63 0912-7984 2022/07 [Refereed]
  • Jun Horita, Shingo Nomoto, Tetsunori Kishikawa, Hiroaki Yamanaka, Shunzo Kawajiri, Seiji Tsuno, Nobuo Takai, Naofumi Nakagawa, Michiko Shigefuji
    BUTSURI-TANSA(Geophysical Exploration) 75 89 - 97 0912-7984 2022
  • Nakagawa N, Takai N, Shigefuji M
    Proceedings of The 14th SEGJ International Symposium DM-P-07  2021/10 [Refereed]
  • Takai N, Tsukamoto A, Nakagawa N, Shigefuji M, Nomoto S, Horita J, Kishikawa T, Kawajiri S, Tsuno S, Yamanaka H
    Proceedings of The 14th SEGJ International Symposium DM-10  2021/10 [Refereed]
  • Site amplification characteristics in the severely damaged area during the;Hokkaido eastern;Iburi earthquake with aftershock records
    Nakagawa N, Takai N, Shigefuji M, Tsutomu S
    Proceedings of the 6th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion GS5-P39  2021/09 [Refereed]
  • Takai N, Shigefuji M
    Proceedings of the 6th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion GS1-I03  2021/09 [Refereed][Invited]
  • Microtremor Explorarions for Shallow S-Wave Velocity Profiles at Strong Motion Stations in Turkey
    Yamanaka, Hiroaki, Chimoto, Kosuke, Ozel, Oguz, Ozmen, Ozgur, Arslan, Safa, Yalcinkaya, Esref, Tun, Muammer, Pekkan, Emrah, Tsuno, Seiji, Kaplan, Onur, Miyake, Hiroe, Tanircan, Gulum, Takai, Nobuo, Ates, Erkan, Tekin, Kudret, Sezen, Ahmet, Ozturk, Taylan, Alkan, Mehmet, Nurlu, Murat, Citak, Seckin, Karagoz, Ozlem, Hatayama, Ken, Ohori, Michihiro, Mirzaoglu, Mete, Sipahi, Ozkan, Morita, Masashi, Sasano, Shiro, Fujita, Yasuhito
    Proceedings of the 17th world Conference on Earthquake Engineering 1f-0013  2020/09
  • Shigefuji M, Takai N, Bijukchhen S, Timsina C, Bhattarai M, Singh S, Miyake H, Koketsu K
    Proceedings of the 17th world Conference on Earthquake Engineering 1d-0048  2020/09
  • Takuho Mori, Michiko Shigefuji, Subeg Bijukchhen, Tatsuo Kanno, Nobuo Takai
    Soil Dynamics and Earthquake Engineering 135 106208 - 106208 0267-7261 2020/08 [Refereed][Not invited]
  • Hiroaki Takahashi, Nobuo Takai, Masahiro Chigira, Guojie Meng, Saeko Kita, Takuji Yamada
    Earth, Planets and Space 72 (1) 2020/05 [Not refereed][Invited]
  • Nobuo Takai, Michiko Shigefuji, Jun Horita, Shingo Nomoto, Takahiro Maeda, Masayoshi Ichiyanagi, Hiroaki Takahashi, Hiroaki Yamanaka, Kosuke Chimoto, Seiji Tsuno, Masahiro Korenaga, Nobuyuki Yamada
    Earth, Planets and Space 71 1880-5981 2019/06 [Refereed][Not invited]
     
    We investigated the cause of destructive ground motion during the 2018 Hokkaido eastern Iburi earthquake. We conducted strong motion observations of aftershocks and microtremors and thesurface wave method in thedamaged areas of the town of Mukawa, Hokkaido prefecture, Japan. The ground accelerations were continuously recorded during a period of approximately 3months after the main shock on September 6, 2018. The heavily damaged buildings were mainly situated around the strong motion station (HKD126) in Mukawa town. Such concentration of damage can be explained by the strong power that was observed in the 1-2 s period of the response spectrum at this station. We estimated the S-wave velocity profiles of this station site and a temporary station site that was installed on a nearby hill. The estimated S-wave velocity, which was inverted from phase velocity structures with the microtremor array and the surface wave method observations explained the difference in the SH-wave amplification characteristics between the two sites. An analysis of HKD126 and the temporarily observed records clearly indicates the strong effects of thelocal geological conditions on the heavily damaged area of Mukawa. The strong ground motion power generated during the main shock in Mukawa for 1-2s periodwas mainly amplified by this shallow underground velocity structure.
  • Michiko Shigefuji, Nobuo Takai, Subeg Bijukchhen, Chintan Timisina, Takuho Mori, Mukunda Bhattarai
    Proceedings of the 13th SEGJ International Symposium, Tokyo, Japan, 12–14 November 2018 2019/04/29
  • Subeg Bijukchhen, Nobuo Takai, Michiko Shigefuji, Masayoshi Ichiyanagi, Tsutomu Sasatani
    Earthquake Spectra 33 S219 - S242 8755-2930 2017/12 [Refereed][Not invited]
     
    A rapid visual damage assessment of buildings around four strong-motion seismic stations in Kathmandu Valley was carried out after the damaging Gorkha, Nepal earthquake (M-w 7.8) of 25 April 2015. The waveforms of the main shock recorded at these stations were compared with the damage to buildings around the stations. The damage was found to be related to strong-motion characteristics of the earthquake. A dominance of long-period oscillation could be observed in the records. The damage to low-rise buildings in the valley was less than anticipated from an earthquake of this magnitude given that the majority of buildings were built without proper engineering consideration. The acceleration response spectra of one of the sedimentary sites show high response in the 1-2 s period range, and nearly 10% of the buildings, which were all low-rise, suffered damage around this site.
  • S. Rajaure, D. Asimaki, E. M. Thompson, S. Hough, S. Martin, J. P. Ampuero, M. R. Dhital, A. Inbal, N. Takai, M. Shigefuji, S. Bijukchhen, M. Ichiyanagi, T. Sasatani, L. Paudel
    TECTONOPHYSICS 714 146 - 157 0040-1951 2017/09 [Refereed][Not invited]
     
    We analyze strong motion records and high-rate GPS measurements of the M 7.8 Gorkha mainshock, M 7.3 Dolakha, and two moderate aftershock events recorded at four stations on the Kathmandu basin sediments, and one on rock-outcrop. Recordings on soil from all four events show systematic amplification relative to the rock site at multiple frequencies in the 0.1-2.5 Hz frequency range, and de-amplification of higher frequencies (>2.5-10 Hz). The soil-to-rock amplification ratios for the M 7.8 and M 7.3 events have lower amplitude and frequency peaks relative to the ratios of the two moderate events, effects that could be suggestive of nonlinear site response. Further, comparisons to ground motion prediction equations show that 1) both soil and rock mainshock recordings were severely depleted of high frequencies, and 2) the depletion at high frequencies is not present in the aftershocks. These observations indicate that the high frequency deamplification is additionally related to characteristics of the source that are not captured by simplified ground motion prediction equations, and allude to seismic hazard analysis models being revised - possibly by treating isolated high frequency radiation sources separately from long period components to capture large magnitude near-source events such as the 2015 Gorkha mainshock. (C) 2016 Elsevier B.V. All rights reserved.
  • Subeg M. Bijukchhen, Nobuo Takai, Michiko Shigefuji, Masayoshi Ichiyanagi, Tsutomu Sasatani, Yokito Sugimura
    EARTH PLANETS AND SPACE 69 (97) 1880-5981 2017/07 [Refereed][Not invited]
     
    The Himalayan collision zone experiences many seismic activities with large earthquakes occurring at certain time intervals. The damming of the proto-Bagmati River as a result of rapid mountain-building processes created a lake in the Kathmandu Valley that eventually dried out, leaving thick unconsolidated lacustrine deposits. Previous studies have shown that the sediments are similar to 600 m thick in the center. A location in a seismically active region, and the possible amplification of seismic waves due to thick sediments, have made Kathmandu Valley seismically vulnerable. It has suffered devastation due to earthquakes several times in the past. The development of the Kathmandu Valley into the largest urban agglomerate in Nepal has exposed a large population to seismic hazards. This vulnerability was apparent during the Gorkha Earthquake (Mw7.8) on April 25, 2015, when the main shock and ensuing aftershocks claimed more than 1700 lives and nearly 13% of buildings inside the valley were completely damaged. Preparing safe and up-to-date building codes to reduce seismic risk requires a thorough study of ground motion amplification. Characterizing subsurface velocity structure is a step toward achieving that goal. We used the records from an array of strong-motion accelerometers installed by Hokkaido University and Tribhuvan University to construct 1-D velocity models of station sites by forward modeling of low-frequency S-waves. Filtered records (0.1-0.5 Hz) from one of the accelerometers installed at a rock site during a moderate-sized (mb4.9) earthquake on August 30, 2013, and three moderate-sized (Mw5.1, Mw5.1, and Mw5.5) aftershocks of the 2015 Gorkha Earthquake were used as input motion for modeling of low-frequency S-waves. We consulted available geological maps, cross-sections, and borehole data as the basis for initial models for the sediment sites. This study shows that the basin has an undulating topography and sediment sites have deposits of varying thicknesses, from 155 to 440 m. These models also show high velocity contrast at the bedrock depth which results in significant wave amplification.
  • Characteristics of Strong Ground Motion in The Kathmandu Valley during the 2015 Gorkha
    Takai N, Shigefuji M, Bijukchhen S, Ichiyanagi M, Sasatani T
    Proceedings of 16th World Conference on Earthquake Engineering 2017/01 [Refereed][Not invited]
  • Features Of Long-Period Ground Motion On The Kathmandu Valley For The 2015 Gorkha Nepal Earthquake Sequence
    Shigefuji M, Takai N, Bijukchhen S, Ichiyanagi M, Sasatani T
    Proceedings of 16th World Conference on Earthquake Engineering 2017/01 [Refereed][Not invited]
  • Strong- Motion Observation And Damage Assessment In Rock And Soil Sites Of Kathmandu, Nepal After April 25, 2015 Gokha Earthquake
    Bijukchhen S, Takai N, Shigefuji M, Ichiyanagi M, Sasatani T
    Proceedings of 16th World Conference on Earthquake Engineering 2017/01 [Refereed][Not invited]
  • Nobuo Takai, Michiko Shigefuji, Sudhir Rajaure, Subeg Bijukchhen, Masayoshi Ichiyanagi, Megh Raj Dhital, Tsutomu Sasatani
    Earth, Planets and Space 68 (1) 1 - 8 1880-5981 2016/12/01 [Refereed][Not invited]
     
    On 25 April 2015, a large earthquake of Mw 7.8 occurred along the Main Himalayan Thrust fault in central Nepal. It was caused by a collision of the Indian Plate beneath the Eurasian Plate. The epicenter was near the Gorkha region, 80 km northwest of Kathmandu, and the rupture propagated toward east from the epicentral region passing through the sediment-filled Kathmandu Valley. This event resulted in over 8000 fatalities, mostly in Kathmandu and the adjacent districts. We succeeded in observing strong ground motions at our four observation sites (one rock site and three sedimentary sites) in the Kathmandu Valley during this devastating earthquake. While the observed peak ground acceleration values were smaller than the predicted ones that were derived from the use of a ground motion prediction equation, the observed peak ground velocity values were slightly larger than the predicted ones. The ground velocities observed at the rock site (KTP) showed a simple velocity pulse, resulting in monotonic-step displacements associated with the permanent tectonic offset. The vertical ground velocities observed at the sedimentary sites had the same pulse motions that were observed at the rock site. In contrast, the horizontal ground velocities as well as accelerations observed at three sedimentary sites showed long duration with conspicuous long-period oscillations, due to the valley response. The horizontal valley response was characterized by large amplification (about 10) and prolonged oscillations. However, the predominant period and envelope shape of their oscillations differed from site to site, indicating a complicated basin structure. Finally, on the basis of the velocity response spectra, we show that the horizontal long-period oscillations on the sedimentary sites had enough destructive power to damage high-rise buildings with natural periods of 3 to 5 s.
  • Masayoshi Ichiyanagi, Nobuo Takai, Michiko Shigefuji, Subeg Bijukchhen, Tsutomu Sasatani, Sudhir Rajaure, Megh Raj Dhital, Hiroaki Takahashi
    Earth, Planets and Space 68 (1) 1 - 6 1880-5981 2016/12/01 [Refereed][Not invited]
     
    The characteristics of aftershock activity of the 2015 Gorkha, Nepal, earthquake (Mw 7.8) were evaluated. The mainshock and aftershocks were recorded continuously by the international Kathmandu strong motion seismographic array operated by Hokkaido University and Tribhuvan University. Full waveform data without saturation for all events enabled us to clarify aftershock locations and decay characteristics. The aftershock distribution was determined using the estimated local velocity structure. The hypocenter distribution in the Kathmandu metropolitan region was well determined and indicated earthquakes located shallower than 12 km depth, suggesting that aftershocks occurred at depths shallower than the Himalayan main thrust fault. Although numerical investigation suggested less resolution for the depth component, the regional aftershock epicentral distribution of the entire focal region clearly indicated earthquakes concentrated in the eastern margin of the major slip region of the mainshock. The calculated modified Omori law's p value of 1.35 suggests rapid aftershock decay and a possible high temperature structure in the aftershock region.
  • Geophysical Exploration of Shallows-Wave Velocity Structure in the Vicinity of Tachikawa-Fault, Japan
    Seita K, Chimoto K, Saguchi K, Tsuno S, Sato H, Matsushima S, Shigefuji M, Takai N, Kanno T, Yamanaka H, Kawase H
    Proceedings of 5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion P210D  2016/08 [Refereed][Not invited]
  • Joint Research on Modeling of Heterogeneous Subsurface Velocity Structure for Evaluating Spatial Variation of Ground Motion Characteristics
    Higashi S, Yamanaka H, Matsushima S, Tsuno S, Takai N, Hayakawa T
    Proceedings of 5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion P208D  2016/08 [Refereed][Not invited]
  • Trial Construction of 1-Dvelocity Structure of the Kathmandu Valley Using the Medium and Large Earthquake Records
    Bijukchhen S, Takai N, Shigefuji M, Ichiyanagi M, Sasatani T
    Proceedings of 5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion 2016/08 [Refereed][Not invited]
  • Features of Ground Accelerations in the Kathmandu Valley during the 2015 Gorkha Nepal Earthquake
    Takai N, Shigefuji M, Bijukchhen S, Ichiyanagi M, Sasatani T
    Proceedings of 5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion 2016/08 [Refereed][Not invited]
  • Characteristics of Long-Period Ground Motion in the Kathmandu Valley from the Large Aftershocks of the 2015 Gorkha Nepal Earthquake.
    Shigefuji M, Takai N, Bijukchhen S, Ichiyanagi M, Sasatani T
    Proceedings of 5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion 2016/08 [Refereed][Not invited]
  • Kobayashi Hiroaki, Koketsu Kazuki, Miyake Hiroe, Takai Nobuo, Shigefuji Michiko, Bhattarai Mukunda, Sapkota Soma Nath
    Earth, Planets and Space Springer 68 (1) 1 - 8 1343-8832 2016/04/26 [Refereed][Not invited]
     
    The 2015 Gorkha earthquake and its aftershocks caused severe damage mostly in Nepal, while countries around the Himalayan region were warned for decades about large Himalayan earthquakes and the seismic vulnerability of these countries. However, the magnitude of the Gorkha earthquake was smaller than those of historical earthquakes in Nepal, and the most severe damage occurred in the north and northeast of Kathmandu. We explore reasons for these unexpected features by performing a joint source inversion of teleseismic, geodetic, and near-field waveform datasets to investigate the rupture process. Results indicate that the source fault was limited to the northern part of central Nepal and did not reach the Main Frontal Thrust. The zone of large slip was located in the north of Kathmandu, and the fault rupture propagated eastward with an almost constant velocity. Changes in the Coulomb failure function (ΔCFF) due to the Gorkha earthquake were computed, indicating that southern and western regions neighboring the source fault are potential source regions for future earthquakes related to the Gorkha earthquake. These two regions may correspond to the historical earthquakes of 1866 and 1344. Possible future earthquakes in the regions are predicted, and the warning for Himalayan seismic hazards remains high even after the Gorkha earthquake.
  • Tsuno S, Chimoto K, Saguchi K, Sato H, Matsushima S, Shigefuji M, Takai N, Kanno T, Yamanaka H, Kawase H
    Proceedings of the 12th SEGJ International Symposium 2015/11 [Refereed][Not invited]
  • Takai N, Shigefuji M, Bijukchhen S, Ichiyanagi M, Sawada K, Rajaure S, Dhital M, Sasatani T
    Proceedings of the 12th SEGJ International Symposium 2015/11 [Refereed][Invited]
  • TAKAI Nobuo, MAEDA Takahiro, SHIGEFUJI Michiko, SASATANI Tsutomu
    Journal of JAEE JAPAN ASSOCIATION FOR EARTHQUAKE ENGINEERING 15 (1) 1_18 - 1_37 1884-6246 2015 [Refereed][Not invited]
     
    We studied characteristics of strong ground motions from the Off-Sanriku outer-rise earthquakes; these earthquakes are activated after the 2011 Tohoku earthquake (<i>Mw</i> 9.0). First, we calculated pseudo velocity responses for five outer-rise earthquakes (<i>Mw</i> 6.0-7.6) and compared them with the attenuation formulae which were constructed for the intraslab earthquake. In spite of outer-rises data being over the distance range of these formulae, the extrapolated formulae generally explained the attenuation relations of these observed data. However, there were considerable residuals between the observed and predicted values. These residuals result from the site and source effects, because the previous attenuation formulae were constructed based on many sites strong motion records from many earthquakes occurring at various source areas. Second, in order to overcome the weakness of the previous attenuation equations, we proposed empirical ground motion prediction equations for a single site; we named these equations "Single-Site GMPE (SS-GMPE)". Our data for regression analysis were strong motion records at a single observation site from the five outer-rise earthquakes occurring at the narrow source area with the radius of about100km. We carried out a regression analysis with respect to <i>Mw</i> for each site assuming the previously estimated internal attenuation for intraslab earthquakes. The earthquake source, propagation path and site effects were well incorporated into these equations, and as a result, the residuals between the observed and predicted values were considerably decreased. Finally, we applied the SS-GMPE to earthquakes not used in the regression analysis and found the good correspondence of predicted and observed spectra.
  • Kawabata W, Sasatani T, Takai N, Shigefuji M
    Proceedings of the 15th Word Conference of Earthquake Engineering 2012/09 [Refereed][Not invited]
  • Sasatani T, Takai N, Shigefuji M, Kawabata W, Okazaki Y, Miyahara Y
    Proceedings of the 15th Word Conference of Earthquake Engineering 2012/09 [Refereed][Not invited]
  • Shigefuji M, Sasatani T, Takai N
    Proceedings of the 15th Word Conference of Earthquake Engineering 2012/09 [Refereed][Not invited]
  • Takai N, Sasatani T, Shigefuji M, Okazaki Y
    Proceedings of the 15th Word Conference of Earthquake Engineering 2012/09 [Refereed][Not invited]
  • SHIGEFUJI Michiko, TAKAI Nobuo, SASATANI Tsutomu
    BUTSURI-TANSA(Geophysical Exploration) 物理探査学会 65 (1) 53 - 66 0912-7984 2012/04 [Refereed][Not invited]
     
    We propose a new method to estimate the path-averaged QS-value at low-frequencies (<0.5 Hz). In this method, we measure the decay rate of the observed S-wave spectral amplitudes against the travel times; the spectral amplitudes are corrected for effects of the S-wave radiation pattern and site amplification due to the deep sedimentary layers. The corrections are done by using the theoretical S-wave spectral amplitudes calculated assuming the perfect elastic body and the appropriate source and site amplification models; the result of this method depends on accuracy of the source and site amplification models. We examine validity of this method and effects of inappropriate source and site amplification models on an estimate of the QS-value. Finally, we apply this method to estimate the QS-value within the back-arc side mantle wedge beneath Kyushu islands. The estimated QS-value is about 50 in the frequency range of 0.2 to 0.3 Hz.
  • 重藤迪子, 高井伸雄, 高橋浩晃, 一柳昌義, 岡島秀樹, 澤田耕助, 宮原有史
    日本地震工学会大会梗概集 8th 260 - 261 2011/11 [Not refereed][Not invited]
  • Yadab P. Dhakal, Tsutomu Sasatani, Nobuo Takai
    PURE AND APPLIED GEOPHYSICS 168 (10) 1599 - 1620 0033-4553 2011/10 [Refereed][Not invited]
     
    The construction of 3-D basin velocity structures is ongoing in many regions of Japan. The structure models are constructed mainly for the prediction of long-period ground motions from future large earthquakes. In this paper, we validate the 3-D velocity structure model of the Tokachi basin, a deep sedimentary basin located in eastern Hokkaido, Japan, based on 3-D simulation of long-period (2-20 s) ground motions from three nearby intermediate-depth earthquakes; this model was constructed by the National Research Institute for Earth Science and Disaster Prevention (NIED). We make comparisons between the observed and synthetic long-period ground motions for the basin-induced surface waves as well as the direct S-wave. We also try to revise the 3-D velocity structure in the western part of the Tokachi basin based on 1-D velocity structures estimated using long-period S-wave modeling and the microtremor survey method. We then perform the 3-D simulation again to validate the revised model. Based on quantitative comparisons of the long-period ground motions from these simulations with those observed, we conclude that the NIED and revised velocity structure models are generally good at the central basin sites, but that both models require modification at the basin edges to explain the details of the observed basin-induced surface waves.
  • Michiko SHIGEFUJI, Tsutomu SASATANI, Nobuo TAKAI
    Proceedings of 4th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion 1 - 9 2011/08 [Refereed][Not invited]
  • Nobuo TAKAI, Tsutomu SASATANI
    Proceedings of 4th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion 1 - 9 2011/08 [Refereed][Not invited]
  • Takahiro MAEDA, Nobuo TAKAI, Tsutomu SASATANI
    4th IASPEI / IAEE International Symposium: Effects of Surface Geology on Strong Ground Motion 1 - 9 2011/08 [Refereed][Not invited]
  • 岡崎由佳, 笹谷努, 高井伸雄, DHAKAL Yadab P
    日本地震工学シンポジウム論文集(CD-ROM) 13th 281 - 288 2010/11 [Refereed][Not invited]
  • 川端渉, 笹谷努, 高井伸雄, 前田宜浩
    日本地震工学シンポジウム論文集(CD-ROM) 13th 275 - 280 2010/11 [Refereed][Not invited]
  • 高井伸雄, 前田宜浩, 笹谷努
    日本地震工学シンポジウム論文集(CD-ROM) 13th 209 - 214 2010/11 [Refereed][Not invited]
  • 前田宜浩, 高井伸雄, 笹谷努
    日本地震工学シンポジウム論文集(CD-ROM) 13th 3580 - 3586 2010/11 [Refereed][Not invited]
  • 重藤迪子, 笹谷努, 高井伸雄
    日本地震工学シンポジウム論文集(CD-ROM) 13th ROMBUNNO.GO4-THU-PM-11  2010/11 [Refereed][Not invited]
  • Yong Cheol Kim, Nobuo Takai
    AIJ Journal of Technology and Design 16 (34) 1123 - 1129 1341-9463 2010/10 [Refereed][Not invited]
     
    The purpose of this paper is to evaluate allocation of evacuation facilities and soft measures to minimize the damage from inland water flooding in Gangnam ward of Seoul city, using evacuation simulation. Simulation was constructed by Multi-Agent-System. The soft measures are measure of disaster weaks, improvement of evacuation start time, and addition of a temporary evacuation facility and divided into 13 combinations. The soft measures were evaluated with time variation of evacuation rate. As a result of simulation, we understood that improvement of evacuation start time, and addition of the temporary evacuation facility were effective.
  • Yadab P. Dhakal, Nobuo Takai, Tsutomu Sasatani
    EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS 39 (4) 443 - 461 0098-8847 2010/04 [Refereed][Not invited]
     
    We study path effects on prediction equations of pseudo-velocity response spectra (natural period of 0.1-5.0 s) in northern Japan, where heterogeneous attenuation structure exists. The path effects have been examined by comparing the regression analysis results for two different prediction equations. The first equation consists of a single term of anelastic attenuation conventionally. The second equation consists of two terms of anelastic attenuation in consideration of the heterogeneous attenuation structure. In the second equation, we divide a source-to-site distance into two distances at the attenuation boundary beneath the volcanic front. The boundary is considered to separate the relatively high Q fore-arc side mantle wedge (FAMW) from the low Q back-arc side mantle wedge (BAMW). Strong motion records (hypocentral distances less than 300 km) from interplate and intraslab events with Mw 5.1-7.3 are used. Regression analysis results show that the standard errors are significantly reduced by the second prediction equation at short periods (0.1-0.5 s), whereas the difference in standard errors from both prediction equations is negligible at intermediate and long periods. The Qs values (quality factor for S-wave) converted from two anelastic attenuation coefficients for the second prediction equation are remarkably similar to the path-averaged Qs values for the FAMW and BAMW by other studies using spectral inversion method. From these findings, we conclude that the path effects on the prediction equation of pseudo-velocity response spectra are satisfactorily accomplished by the second prediction equation. Copyright (C) 2009 John Wiley & Sons, Ltd.
  • 前田 宜浩, 高井 伸雄, 笹谷 努
    Geophysical bulletin of Hokkaido University 北海道大学大学院理学研究院自然史科学部門（地球物理学） 0 (73) 217 - 227 0439-3503 2010/03 [Not refereed][Not invited]
     
    The largest aftershock（Mw 7.3）of the 2003 Tokachi-oki earthquake（Mw 8.3）generates larger peak ground acceleration（PGA）values than the main shock in the western side of the epicenters despite their magnitude difference. We study the features of strong ground motions from the largest aftershock in detail using PGA values. Spatial distribution maps of PGA ratio between the largest aftershock and adjacent earthquake shows obvious azimuth dependency compared with the other earthquake pairs occurring around Japan. Attenuation relationship of the largest aftershock shows a large azimuth-dependent ...
  • 三輪田吾郎, 高井伸雄, 清水学, 笹谷努, 前田宜浩, 山本明夫
    Geophysical bulletin of Hokkaido University 北海道大学大学院理学研究院自然史科学部門（地球物理学） 0 (73) 195 - 205 0439-3503 2010/03 [Not refereed][Not invited]
     
    Nonlinear site response was observed at TKCH 07 in Toyokoro and HKD 109 in Urakawa during the mainshock（Mj 8.0）and the largest aftershock（Mj 7.1）of the 2003 Tokachi-oki Earthqua ke． At TKCH 07, peak ground acceleration（PGA）was smaller than PGA at the other strong motion station in Toyokoro. At HKD 109, the accelerogram shows a characteristic spiky waveform. Due to this spiky wave, large PGA was observed compared to the other stations in Urakawa, although PGA at HKD 109 was smaller than PGA at JMA Urakawa station during the main shock and smaller aftershocks.
  • Dhakal P, Sasatani T, Takai N
    Proceedings of the 9th SEGJ International Symposium -Imaging and Interpretation- 0112  2009/10 [Refereed][Not invited]
  • Dhakal P, Sasatani T, Takai N
    Proceedings of the 14th Word Conference of Earthquake Engineering 0023  2008/10 [Refereed][Not invited]
  • Takai N, Sasatani T
    Proceedings of the 14th Word Conference of Earthquake Engineering No.1052  2008/10 [Refereed][Not invited]
  • Kizuku Miyakoshi, Nobuo Takai, Hiroshi Kagami
    AIJ Journal of Technology and Design 社団法人日本建築学会 14 (27) 343 - 346 1341-9463 2008/06 [Refereed][Not invited]
     
    In the previous paper, damage of seven earthquakes occurred in the offshore and inland areas of Hokkaido Hidaka province were surveyed and detailed damage were clarified by each municipalities. In this paper, surveyed earthquakes were expanded to those reported greater than 4 in JMA intensity scale in Urakawa town, the central town of Hidaka province. Totally 70 earthquakes from 1901 to 2006 were picked up and literature surveys were performed through damage reports and newspaper articles. Among them, 22 earthquakes caused damage in Urakawa town and detailed damage by local units were listed and mapped. Damage distribution was discussed in relation with historical formation and soil conditions and vulnerable areas can be revealed.
  • OHATA Daishiro, TAKAI Nobuo, KAGAMI Hiroshi
    Journal of architecture and planning 社団法人日本建築学会 0 (612) 87 - 91 1340-4210 2007/02 [Refereed][Not invited]
     
    In the previous study, a simulation model of evacuation from tsunami for the region where the refuge was easy to the upland was proposed utilizing Multi Agent System. On the other hand, numerous flat lowland cities exist in the coastline in Japan, moreover in those area the distribution of Tsunami refuge facilities is important. In this study, the model was applied to Kushiro City's urban central district as example of the coastal plain city. Several present problems in this district were indicated, through spatial evaluation of Tsunami refuge facilities.
  • TABATA Naoki, OKADA Shigeyuki, TAKAI Nobuo
    Journal of Structural and Construction Engineering (Transactions of AIJ) 日本建築学会 72 (611) 39 - 46 1340-4202 2007 
    We know the fact that almost all the people are killed by collapsed wooden houses in earthquake, but a precise estimation method for casualties hasn't existed in the field of earthquake engineering. In this paper we reconstruct the vulnerability function and damage index function for wooden building in order to estimate damaged building under the state that many people are killed. Combination of this function and Death Risk Function gives us the preventive information for individual and the precisely estimated casualties in wide areas for municipal prevention project.
  • SASATANI Tsutomu, MAEDA Takahiro, TAKAI Nobuo
    Geophysical exploration 物理探査学会 59 (4) 315 - 326 0912-7984 2006/08 [Refereed][Not invited]
  • 岡田成幸, 高井伸雄, 島田佳和
    日本地震工学シンポジウム論文集(CD-ROM) 12th ROMBUNNO.0237  2006 [Refereed][Not invited]
  • 前田宜浩, 高井伸雄, 笹谷努
    日本地震工学シンポジウム論文集(CD-ROM) 12th ROMBUNNO.0356  2006 [Refereed][Not invited]
  • 三輪田吾郎, 高井伸雄, 清水学, 前田宜浩, 笹谷努
    日本地震工学シンポジウム論文集(CD-ROM) 12th ROMBUNNO.0095  2006 [Refereed][Not invited]
  • 高井伸雄, 前田宜浩, 笹谷努
    日本地震工学シンポジウム論文集(CD-ROM) 12th ROMBUNNO.0334  2006 [Refereed][Not invited]
  • 玉川奈都子, 大畑大志郎, 高井伸雄, 鏡味洋史
    日本地震工学シンポジウム論文集(CD-ROM) 12th ROMBUNNO.0293  2006 [Refereed][Not invited]
  • 前田 宜浩, 笹谷 努, 高井 伸雄
    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科地球惑星科学専攻（地球物理学） 0 (68) 141 - 152 0439-3503 2005/03 [Not refereed][Not invited]
  • Maeda, T., Sasatani, T., Takai, N., Shimizu, G.
    Journal of the Hokkaido University, Faculty of Science, Series VII: Geophysics (68) 0441-067X 2005
  • Tabata N, Takai N, Okada S
    Proceedings of 13th World Conference on Earthquake Engineerin 729  2004/08 [Refereed][Not invited]
  • Okada S, Takai N
    Proceedings of the 13th Word Conference of Earthquake Engineering 728  2004/08 [Refereed][Not invited]
  • Takai N, Shimizu G, Okada S
    Proceedings of the 13th Word Conference of Earthquake Engineering 731  2004/08 [Refereed][Not invited]
  • 岡田成幸, 高井伸雄
    日本建築学会構造系論文集 日本建築学会 69 (582) 31 - 38 1340-4202 2004/08 [Refereed][Not invited]
     
    This paper discussed Damage Index Function by which damage state of individual building can be estimated. and proposed the method for deducing the functions with structural parameter of the load-carrying capacity fbr buildings. We can apply the 3D nomograms of the obtained functions with three different types of parameters to utilize for various kinds of seismic risk management; for example, damage evaluation of individual building for an assumed earthquake, estimation of the standardized strength of buildings in regions not for generating damages. and stochastic estimation of return period on regional input motions that give rise to devastating damages to buildings.
  • 高井伸雄, 岡田成幸
    日本地震工学シンポジウム論文集 11th 605 - 608 2002/11 [Refereed][Not invited]
  • 岡田成幸, 高井伸雄, 太田洋芳
    日本地震工学シンポジウム論文集 11th 2087 - 2090 2002/11 [Refereed][Not invited]
  • 高井伸雄, 岡田成幸
    日本建築学会構造系論文集 (549) 67 - 74 1340-4202 2001/11 [Refereed][Not invited]
  • 高井伸雄, 岡田成幸, 高井博雄, 宮野道雄, 鈴木有
    日本建築学会技術報告集 06 (10) 305 - 308 0003-8555 2000/06 [Refereed][Not invited]
  • TAKAI Nobuo, OKADA Shigeyuki, TAKAI Hiroo, MIYANO Michio, SUZUKI Tamotsu
    AIJ Journal of Technology and Design 日本建築学会 6 (10) 305 - 308 1341-9463 2000 
    In order to quantitatively describe features on building structure damage, we classified about 650 dwellings into 23 damage patterns by using a photographic database of building damage in Hokudan-cho, Awaji Island due to the 1995 Hyogo-ken Nanbu earthquake. On the basis of the data, the relationship between building damage and human casualty was investigated, and the dangerous building damage pattern was specified. In addition, restoration situation passing through 3 or 4 years after the earthquake was the result that most of renewed dwellings had been adopted aseismic construction style.
  • The Useful Method of Predicting Seismic Ground Severity for Subduction Zones
    Takai N, Umeda H, Okada S
    Proceedings of the 12th Word Conference of Earthquake Engineering 760  2000/01 [Refereed][Not invited]
  • Classifications of Structural Types and Damage Patterns of Buildings for Earthquake Field Investigation
    Okada S, Takai N
    Proceedings of the 12th Word Conference of Earthquake Engineering 705  2000/01 [Refereed][Not invited]
  • 岡田成幸, 高井伸雄
    日本建築学会構造系論文集 (524) 65 - 72 1340-4202 1999/10 [Refereed][Not invited]
  • 岡田成幸, 高井伸雄
    日本地震工学シンポジウム論文集 10th 3235 - 3240 1998/11 [Refereed][Not invited]
  • 高井伸雄, 梅田浩士, 岡田成幸
    日本地震工学シンポジウム論文集 10th 553 - 558 1998/11 [Refereed][Not invited]
  • Seismic Microzonation of Coastal Hillside City: a Case Study in Otaru, Hokkaido, Japan
    Takai N, Kagami H
    Proceedings of the 11th Word Conference of Earthquake Engineering 1759  1996/06 [Refereed][Not invited]
  • Seismic Hazard Maps of Hokkaido, Japan, Based on the Data of Questionnaire Intensity Surveys.
    Kagami H, Okada S, Takai N
    Proceedings of the 11th Word Conference of Earthquake Engineering 1773  1996/06 [Refereed][Not invited]
  • 鏡味洋史, 岡田成幸, 高井伸雄
    日本地震工学シンポジウム論文集 9th (Pt 1) 139 - 144 1994/12 [Refereed][Not invited]

Books etc

Presentations

Association Memberships

  • American Geophysical Union   Society of Exploration Geophysicists   THE SOCIETY OF EXPLORATION GEOPHYSICISTS OF JAPAN   日本地震工学会   米国地震工学会(Earthquake Engineering Research Institute)   米国地震学会(SEISMOLOGICAL SOCIETY of AMERICA)   JAPAN SOCIETY FOR NATURAL DISASTER SCIENCE   地域安全学会   日本地震学会   Architectural Institute of Japan   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2022/04 -2026/03 
    Author : 山中 浩明, 高井 伸雄, 松島 信一, 地元 孝輔, 山田 伸之, 神野 達夫, 笠松 健太郎
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
    Date (from‐to) : 2020/10 -2025/03 
    Author : 高井 伸雄, 越川 武晃, 重藤 迪子
     
    2020年度に引き続き，現地共同研究者と共にカトマンズ盆地内のバクタプル市および周辺の地質学的情報および，地震記録の資料収集を実施している．社会情勢により現地渡航が叶わなかったが，現地共同研究者と現地での強震観測設置に関しての議論をオンライン等で実施し，2020年度に導入した地下構造探査用の高感度地震計を国内のテストフィールドで引き続き操作性等を確認した．カトマンズ盆地内には申請者らがこれまでに計14点の強震観測点を設置してきた．それらの観測点で過去に蓄積された強震観測データの分析を通して，盆地内の地盤増幅特性の違いを指摘した．2021年9月に仙台で開催された第17回世界地震工学会議の特別セッションにおいて，オンライン参加の現地カウンターパートを含め，2015年ゴルカ地震以降のカトマンズ盆地周辺の強震動研究に関する討議を実施した．また，これまでに蓄積してきた2015年ネパール・ゴルカ地震とその余震等の強震記録にレシーバー関数を適用して，カトマンズ盆地の代表者と現地共同研究者らが過去に8観測点から推定した地下構造モデル(Bijukchhen et al., 2017, Bijukchhen, 2018)の再検討を実施し，その成果も同会議にて発表している．具体的には14観測点の各波形のP波到達時刻から3秒間の記録に対して，1-10Hzのバンドパスフィルターを用いて，レシーバー関数を求め，Phase-weighted stacksにより複数の余震記録に対してスタッキング処理を実施した．スタッキング処理により得られた最終的なレシーバー関数から見られるPs-P時間は，前出の地下構造モデルによる各観測点直下の地震基盤深さと良く対応している事が明らかとなった．さらに，理論レシーバー関数を計算したPs-P時間と観測記録により得られたPs-P時間を比較することによりP波速度の検討を実施した．
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2020/04 -2025/03 
    Author : 高井 伸雄, 越川 武晃, 前田 宜浩, 地元 孝輔, 神野 達夫, 重藤 迪子
     
    【地震動・地下構造・地震被害データベース構築】2018年北海道胆振東部地震の余震を含めた強震記録の整理，日本海溝・千島海溝付近のプレート境界およびプレート内で発生する地震に対して周波数毎の励起特性の分析等を実施した．観測点の浅部地下構造探査の精度の確認のため，2020年10月から実施している北見市における7点同時微動アレー探査と表面波探査を継続した．夏期と冬期の変化に加え，表層の乾燥状態によっても，表面波探査結果が異なる事が示された．2021年10月より北見市内で地点を変え，25cmの受振器ピッチで72chの同時観測により，高密度表面波探査を実施し浅部探査結果の季節変動に関する検討を行った．夏期と比較して厳冬期はレイリー波の位相速度が高くなることが確認出来，表層地盤の速度構造探査の問題点等が指摘でき，地震動の高周波数側への影響把握の基礎データが蓄積された． 【2018年北海道胆振東部地震の震央付近の1次元地下構造モデルの構築】推定済みであるHKD126観測点に加え，前年度に引き続き，震度7が記録された気象庁鹿沼観測点から直後に臨時余震観測点を設置した地域に，本年度は長周期の地震動が卓越したと思われる浜厚真余震観測点HUE05を加え，地震記録を用いた自己相関関数等の解析を実施し，既存の地下構造モデルの検討を実施した．既往の地下構造でも震央付近は非常に基盤構造が複雑であり，それぞれの観測点の記録に対して実施した自己相関関数解析においては，観測点から震央への方位角により，自己相関関数のピーク位置が異なることを明らかにし，今後の傾斜面の把握等の基礎資料を得た． 【2018年北海道胆振東部地震の震源モデルの構築】既往の震源インバージョン結果を整理し，余震記録を用いて経験的グリーン関数法により，非線形性を考慮した上で，本震時の震央周辺の記録の再現に着手した．
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2023/03 -2024/03 
    Author : 楠 浩一, 青木 陽介, 西村 卓也, 小林 知勝, 近藤 久雄, Adriano Bruno, 王 功輝, Bhandary NetraPrakash, 加藤 愛太郎, 山本 揚二朗, 吉田 圭佑, 八木 勇治, 内田 直希, 汐見 勝彦, 山中 浩明, 高井 伸雄, 吉見 雅行, 地元 孝輔, 中村 洋光, 目黒 公郎, 久田 嘉章, 森 伸一郎, 清田 隆, 小野 祐輔, 後藤 浩之, 日比野 陽, 毎田 悠承, 大西 直毅, SHEGAY ALEKSEY, 阪本 真由美, 金田 義行, 木村 周平, 牧 紀男
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Pioneering)
    Date (from‐to) : 2017/06 -2021/03 
    Author : Takai Nobuo
     
    The source characteristics of plate boundary earthquakes and inland crustal earthquakes have been examined in detail due to their frequency. But there is a small number of examples of intraplate earthquakes. We compared the source characteristics of interplate and intraplate earthquakes of almost the same scale and epicenter and showed that high-frequency excitation in intraplate earthquakes is strong. We also compared intraplate earthquakes with different depths and showed that deep hypocenters have stronger high-frequency excitation than shallow hypocenters. The 2018 Hokkaido Eastern Iburi Earthquake was relatively deep and had strong high-frequency excitation source characteristics. We estimated the underground structural model around the area where the dangerous seismic motion occurred, was estimated. We clarified that the causes of dangerous seismic motion are the ground amplification characteristics of the surface layer and the non-linear effect during the mainshock.
  • 科学技術振興機構－国際協力機構：国際科学技術共同研究推進事業 地球規模課題対応国際科学技術協力プログラム（SATREPS）
    Date (from‐to) : 2015 -2021 
    Author : 纐纈一起
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Special Purposes
    Date (from‐to) : 2018/10 -2019/03 
    Author : Takahashi Hiroaki
     
    Comprehensive investigation on the 2018 Hokkaido Eastern Iburi earthquake and its disaster was conducted. Mainshock rupture initiated at deepest part and major slip was occurred in 20-30km deep. Multiple simultaneous landslides in Atsuma town was induced by combination of strong ground shaking and weak sliding layer between pyroclastic fall deposit layers. Halloysite cray minerals was discovered in all sliding layers. Simulation suggested landslides might attack residential houses within 6 seconds. Observed peak ground motions in nearby area were larger than common distance attenuation model. Severe wooden house damage in Mukawa town was due to amplified seismic waves due to site effects. Sounding and boring investigation revealed filled low-density volcanic ash and higher groundwater level in liquefaction area. Electricity blackout caused severe damage in social and economic activities of Hokkaido. These scientific outcomes were explained to residents at public briefing session.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2016/04 -2019/03 
    Author : Shigefuji Michiko, TAKAI Nobuo, BIJUKCHHEN Subeg
     
    Generally, the strong ground motion is strongly affected by the sedimentary basin. Slip pulse motions are generated when the seismic source fault is located near the seismic station. In this study, we explored the generation mechanism of the slip pulse motion which is observed on the rock site in the Kathmandu Valley during the 2015 Gorkha Nepal earthquake. We revealed that this slip pulse motion is largely affected by the near-field and the intermediate terms from the nearest slip area and amplified by the basin.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2016/04 -2019/03 
    Author : Hisada Yoshiaki, Kudo Kazuyoshi, Irikura Kojiro, Yokota Takashi, Tanaka Shinya
     
    First, we clarified that the long-period pulse ground motion observed by the Nepal Gorkha earthquake was the ground motion from the source fault of about 10 km depth and amplified in the sedimentary basin. Next, we derived the empirical constitutive law of the slip rate function considering the fling step generated from the region shallower than the seismogenic layer, and constructed a prediction model to improve the conventional strong motion prediction recipe. Furthermore, we confirmed the reproducibility of the observation records near large-scale active fault earthquakes such as the 2016 Kumamoto earthquake, the 1999 Kocaelli earthquake, and the 2008 Chi-Chi earthquake, and verified the validity of the method. Finally, we examined effective seismic reinforcement in high-rise buildings by considering long-period ground motions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Special Purposes
    Date (from‐to) : 2015/05 -2016/03 
    Author : YATABE RYUICHI, FUKUOKA Hiroshi, HIGAKI Daisume, Bhandary N. P., HASEGAWA Shuichi, KAMIISHI Isao, IZUMI Kaoru, SATO Hiroshi, TAKAI Nobuo, KUMAHARA Yasuo, MIO Minoru, TAKADA Yosuke, TAKEUCHI Yasushi, OKUBO Takeyuki, MINAMI Makito, ATSUMI Tomohide, MURAKAMI Hitomi, YAGI Hiroshi, MOMOMURA Atsuko, YAMAGUCHI Satoru, KAWASHIMA Katsuhisa, HIRATA Nao, SAKAI Shinichi, KURASHIMO Eiji, KOKETSU Kazuki, SHIGEFUJI Michiko, ISHIYAMA Tatsuya, MATSUTA Nobuhisa, HIROUCHI Daisuke
     
    In this study, we conducted a comprehensive investigation of the damage made by Nepal Gorkha Earthquake occurred on 25 April 2015. The main items of understandings of the investigation and analysis are: 1) earthquake occurrence mechanism , 2) mechanism of slope failures in the mountainous areas due to the earthquake and fault activities, 3) situation of damage and destruction of buildings and civil infrastructures, 4) situation analysis of earthquake-induced ice avalanche disaster, and 5) overall disaster risk assessment. Through these items of understanding, we contributed to second-stage disaster reduction and restoration plan preparation in Nepal.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2013/04 -2016/03 
    Author : TAKAI Nobuo
     
    There were considerable residuals between the observed and predicted values. These residuals result from the site and source effects, because the previous attenuation formulae were constructed based on many site’s strong motion records from many earthquakes occurring at various source areas. In order to overcome the weakness of the previous attenuation equations, we proposed empirical ground motion prediction equations for a single site; we named these equations “Single-Site GMPE (SS-GMPE)”. We carried out a regression analysis with respect to MW for each site assuming the previously estimated internal attenuation for intraslab earthquakes. The residuals between the observed and predicted values were considerably decreased. We applied the SS-GMPE to earthquakes not used in the regression analysis and found the good correspondence of predicted and observed spectra.
  • 科学技術振興機構：国際緊急共同研究・調査支援プログラム（J-RAPID）
    Date (from‐to) : 2015 -2016 
    Author : 纐纈一起
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2011/04 -2014/03 
    Author : TAKAI NOBUO
     
    I tried the strong motion evaluation of the Katmandu Basin that was the world heritage area of the Nepalese country. I evaluated basement structure in cooperation with an expert of the local geological feature, seismology. I started strong motion observation inside and outside of the basin. I estimated the shallow underground structure near the observation sites by the surface wave exploration method. High quality strong motion data was recorded in each site. I could confirmed these time series data and spectra with the shallow underground structure for each sites. These data which were recorded in Katmandu Basin and a penumbra for the first time will be important basics data to a strong motion prediction in the future.
  • 単一サイト強震動予測式(SS-GMPE)の精度向上のための予測残差要因の分析
    戸田育英財団：
    Date (from‐to) : 2014 -2014 
    Author : 高井 伸雄
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2009 -2012 
    Author : KAWASE Hiroshi, KAMAE Katsuhiro, IWATA Tomotaka, YAMANAKA Hiroaki, SATOH Toshimi, SASATANI Tsutomu, TAKAI Nobuo, NOZU Atsushi, MATSUSHIMA Shinichi, KATO Kenichi, FUJIWARA Hiroyuki, SEKIGUCHI Haruko, SAKAI Yuki, HO Naranmandora
     
    To evaluate disaster risk from predicted ground motions for majorcities in Japan, we propose a systematic method to delineate hypothesized sources, aunified prediction scheme for strong motions, an evaluation method of building damageusing the response simulator. We also propose a various up-grading techniques for morequantitative strong motion prediction based on the data from the 2011 Tohoku earthquake.
  • 常時微動観測を用いたカトマンズ盆地における強震動観測点の地震動特性評価
    大林財団：国際交流助成
    Date (from‐to) : 2011 -2011 
    Author : 高井 伸雄
  • ネパール国カトマンズ盆地における地震防災対策立案のための強震動評価に関する研究
    平和中島財団：アジア地域重点学術研究
    Date (from‐to) : 2011 -2011 
    Author : 高井 伸雄
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2007 -2010 
    Author : KOKETSU Kazuki, HORI Muneo, MIYAKE Hiroe, IRIKURA Kojiro, KUDO Kazuyoshi, MIDORIKAWA Saburoh, TAKAI Nobuo, IWATA Tomotaka, KAEWASE Hiroshi, KAMAE Katsuhiro, TAKENAKA Hiroshi, HISADA Yoshiaki, AOI Shin, FURUMURA Takashi, SASATANI Tsutomu, SEKIGUCHI Haruko, FUKUWA Nobuo, ZAMA Shinsaku, FUJIWARA Hiroyuki, HIGASHI Sadanori
     
    Toward seismic hazard assessment for long-period ground motion, this study integrates four research components of seismic source, velocity structure, numerical simulation, and damage and risk. We then create the Japan Integrated Velocity Structure Model, and long-period ground motion hazard and risk maps.
  • 保育所における防犯・防災性能の向上に関する研究
    セコム科学技術振興財団：
    Date (from‐to) : 2006 -2006 
    Author : 高井 伸雄
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2004 -2006 
    Author : SASATANI Tsutomu, KAGAMI Hiroshi, TAKAI Nobuo, OKADA Shigeyuki, ISHIKAWA Hiroyuki, SATOH Takashi
     
    The 2003 Tokachi-oki earthquake, a great interplate earthquake (Mw8.3), is the first M8 class earthquake in Japan since the dense strong-motion networks such as the K-NET and KiK-net have been deployed. We examine spatial distributions of velocity responses (damping factor h=0.05) with various natural periods for this earthquake by using the dense strong-motion network data. The short-period (T=0.1sec; T=natural period) velocity response distribution shows a typical feature for subduction-zone earthquakes; the high response values are observed along the Pacific coast of north Japan. This feature is explained by the S-wave attenuation structure beneath north Japan; that is, the path effect. On the other hand, the long-period (T=20sec) velocity response distribution shows a peculiar feature: at comparable distance, the response values in the northern part of the epicenter are higher than those in the south-western part. This peculiar feature is mainly explained by the source effect; the radiation pattern of long-period Rayleigh waves. We find various types of the site effects. A remarkable one is excitation of long-period basin surface-waves at large plains with thick sedimentary layers. The other remarkable one is nonlinear site response. We find mild nonlinear site response at a soft soil site located on flood plain deposits; the nonlinearity is confirmed by comparing the transfer functions for weak and strong motions using the downhole array data. The distinctive nonlinearity is also observed at a not-so-soft soil site located on reclaimed land during the largest aftershock; the accelerogram shows a spiky waveform.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2004 -2005 
    Author : 高井 伸雄
     
    本研究は保育所の防災・防犯における問題点を整理し,解決策を探るものである.防災に関しては,日常災害,地震災害と火災を主に扱い防犯に関しては部外者侵入の抑制に関して検討を加えた.16年度から引き続き,保育所における災害・犯罪に関して,医療現場や建設現場で良く用いられる事故には至らない「ひやり・はっと」事象の収集を行った.父兄からは,直接入力ではなく,紙ベースでのアンケート形式によりヒヤリハットデータの回収協力を得られた.その中でも,事故に至らずとも,非常に危険な事例が多く見られた.今年度はさらに,実際に事故に至った事例も収集した.防災・防犯対策に固執することで,ソフト・ハードの両面が無機的なものとならないよう,園児の知育発達の側面から保育所施設・運営計画を研究した事例等を参考にするべきであるが,昨年度,新築保育所の計画・設計に立ち会う機会を設け,内容を保育士・父兄と議論する機会を得ることができた.その新築保育園の完成に伴い,新築保育園における,育児環境,児童行動状況の把握を行うことを試みた.新築保育園における調査は主に,保育士からのアンケート・ヒアリングにより,事故事例・ひやりはっと事例の収集を行った.それにより,高学年児童と低学年児童のゾーニングが反映された平面計画は非常に保育環境としては優れているものの,全体の集中管理に関しては若干の課題を残していることが判明した.このことは,他の事例からも,ハード的は解決が得られていくものであると考えられる. 収集事例の保育士へのフィードバックを行った結果,事故事例の収集においては,幸い大事には至らなかったものの,子供特有の行動パターンから,ハード的解決をもっても限界が存在する事例に関し,ソフト的(教育的)な解決を得なければ,将来的にも起こりうるであろうとの,保育士からのコメントを得ることが出来た.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2002 -2004 
    Author : OKADA Shigeyuki, TAKAI Nobuo, KIYONO Junji, WATOH Yukihiro, ISHIYAMA Yuji, KAGAMI Hiroshi, AOKI Noriaki, SMITH Jack W., DUNN Kim
     
    (1)Research background To uncover the mechanism of human injury in buildings damaged by devastating earthquakes is indispensable to the fundamental resolution for prevention of the occurrence of deceased. However, conventional studies formulate the death toll estimation directly from the number of building collapses. Such ridiculous situation would be caused by the fact that there has been no contact in the research field between building structural engineers and disaster medical researchers, and they have been advancing the research under the independent organization each other. (2)Objectives of the project In order to interdisciplinary discuss the latest results of the research of the earthquake engineering and the disaster medicine. By the application of regression analysis and some statistical work to the database the study secondly tries to propose the death toll estimation model that runs to concrete measures for the human damage reduction. In this project treats the 2004 Barn Earthquake in Iran as an earthquake with masonry structure collapse, the 1999 Kocaeri Earthquake in Turkey as an earthquake with RC structure collapse, and the 1995 Kobe Earthquake in Japan as an earthquake with wooden structure collapse. (3)Implementation of the project Kickoff meeting : To discuss the research plan for 3 years with the researchers in the engineering field and the medical field at the first stage, an interdisciplinary symposium for research exchange was executed by the Japan-U.S.cooperation at the Center for Health Science, the University of Texas. The symposium was held by opening to the public, and the state of the symposium was simultaneously dlelivered to the world through the Internet Web. Construction of database : Based on the discussion in the symposium, the definition of building damage was redefined from the viewpoint of death occurrence in seismic damage building for the purpose of database construction for clarifying the death occurrence mechanism. The new definition was visualized as a pattern chart of building damage. Following the definition, we rebuilt the database from the information about dead and damage to building in the Kocaeri Earthquake and the Kobe Earthquake. In addiiton, we consolidated the database by adding the concerning data which various research organizations had collected. Modeling death toll estimation and its application : We elucidated the death causalities by means of event tree analysis for the Kobe Earthquake's database. On the basis of the result, a causal model following the process to death was proposed. That is to say, the death toll estimation model was constructed in multivariate regression model, in which the structural damage pattern of building can be specified as the result for given earthquake ground motion severities at the first step, the volumetric loss of building can be counted by the spatial damage index at the second step, and then the survival rate of inhabitants entrapped in collapsed building can be calculated at the final step. This model is not only accurate in comparison with the conventional simple models, that the collapse of building regulates the number of killed people, but also applicable to various type of buildings in foreign countries by introducing the index of volumetric loss. In addition, this model can help the decision-making for the optimal triage for search and rescue (SAR) activities as a post countermeasure ; because the survival potential of trapped people in collapsed building is affected strongly by the collapsed pattern of building, and the model can provide the information about the collapsed pattern.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2002 -2003 
    Author : 高井 伸雄
     
    これまでに提案してきた破壊パターンは内部空間の損失を反映した指標であるが、さらに定量的に評価するために、内部空問の損失を評価するW-値を導入し、建物の破壊パターンとW-値との関係を明らかにした。ここで、人的負傷とを関連づけることで、建物被害とは独立した、人間への外力と傷害度との関係が導き出される。ここでは人間の負傷度を医学で用いられる指標(傷害度スコア)を引用し、医学研究者との議論を重ね、内部空間損失と人的負傷との関係を明らかにした。 以上で地震時の建物被害による人的被害発生のメカニズムが明らかになったが、パターンと傷害度スコアとの関係は、東灘区のデータを利用していることから、一般化を目指し他地域での適用に関して議論した。そこで、対象地域を木造パラメーターの異ならないと思われる地域として、同地震で被害を受けた神戸市長田区を新たに対象地域都市として、GIS上に同様のデータベースを構築し、人的被害を予測した。その結果これまでに利用されてきた手法より精度の高い予測が可能となっている。これまでは木造に関しての解析であるが、1999年トルコ地震におけるRC建物造に関しての建物破壊パターンとW値との関係も議論可能とするべく、一次解析としてRC造の破壊パターンと主要な破壊階と死傷者の関係のデータベースを構築した、RCに関してはさらに詳細な解析を行う準備がある。 ここで注目する点は精度の向上よりも、メカニズムに踏み込んだ議論をしていることであり、以上により明らかとなった木造建物の地震被害による人的被害発生メカニズムを基に、より安全性の高い破壊パターンを考慮した建物形式、及び既存不適格建物の補強方法を議論することが可能となった。
  • 広域地震被害予測のための高精度地震動分布予測手法の開発
    セコム科学技術振興財団：
    Date (from‐to) : 2000 -2001 
    Author : 高井 伸雄
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Young Scientists (A)
    Date (from‐to) : 2000 -2001 
    Author : 高井 伸雄
     
    北海道の太平洋プレート境界付近で発生する複数の地震に関し、プレート内・プレート以浅、それぞれの地震波伝播経路長を説明変数、地震動強さを目的変数として、関係式を回帰分析により求めた。求められた関係式はおおよそ基盤における地震動分布予測式と考えてよい。また、回帰式と観測値の差を国土数値情報により議論した。 各地震により求められた、回帰式の係数を目的変数、マグニチュードを説明変数とし、再度回帰式を求めた。この回帰式が、任意の地震、観測点に対して地震動を予測する距離減衰式に相当する。この回帰に際し、震源距離のみをパラメータとした減衰式も作成したが、回帰係数が、本手法と比較し低いことが確認でき、これは本手法が伝播経路の影響を考慮できている為であると理解できる。以上により北海道における広域地震動分布予測式を作成した。 次に、求めた予測式を他地域に拡張して議論した。日本付近のプレートの沈み込みを北海道地域同様に既往の研究を基にモデル化し、過去の地震による震度分布や強震動データを用い、予測式の汎用性を検証した。特に東北地方では、同様のプレート沈み込み形状を有しており、予測精度が高いことが確認出来た。 求められた予測式と、震度に対する被害関数を用い、北海道をテストフィールドとして想定地震に対する被害予測を実施した。この被害予測の結果と、既往の距離減衰式による予測結果とを比較し、考察を加えた。本手法による被害予測結果は、より実際の被害に近く、想定地震に対する、防災計画等への援用に有用であることが明らかとなった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2000 -2001 
    Author : SASATANI Tsutomu, TAKAI Nobuo, KAGAMI Hiroshi, KASAHARA Minoru, ANDO Fumihiko, HAYAKAWA Fukutoshi
     
    We have developed a simple method for installing a deep borehole seismometer inside a preexisting well. The developed points are (1)double-casing system down to the well-bottom to protect effects due to well-water movement, (2)boring at the bottom of the preexisting well to install the borehole seismometer, (3)damping system to protect vibration noises propagating the inner casing, and (4)use of an optical fiber cable to transmit the digital data. Our system is easy to install and take up the borehole seismometer. We have confirmed our system comparing the seismograms with those by the other borehole seismometers. Micro-earthquake activity beneath Sapporo urban districts has been studied based on data from several borehole seismometers. The epicentral distribution shows a linear trend with the NW-SE direction ; this might represent a blind fault beneath Sapporo urban districts. Finally we have studied the seismic response of sedimentary layers based on surface and borehole seismic data.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Young Scientists (A)
    Date (from‐to) : 1998 -1999 
    Author : 高井 伸雄
     
    広域地震防災対策の基礎資料として重要な想定地震における広域震度分布図を、精度高く予測するために、地球内部の減衰構造を反映させて作成する手法を開発している。被害地震で得られたアンケート震度データを、大規模減衰構造である太平洋プレートの沈み込み形状を踏まえて解析を行った。 (1)サイスミックレイトレーサーの作成と伝播経路の計算及び回帰式の作成 既往の2重深発地震面に関する研究を基に、北海道地域の太平洋プレートの沈み込み形状をプレートとそれより上部という2層にモデル化した。作成したモデルを基に観測点と震源を含む断面を作成し、スネルの法則を用いて2次元内の地震波伝播経路を求める。本年度は、前年度よりさらに広域、高密度に展開するため、経路を求めるためのレイトレーサーを作成し、このレイトレーサーを用いて伝播経路を求めた。求められる伝播経路はプレート内とそれより上部となる。震度を目的変数、求めた経路を2つの説明変数として各地震で回帰式を求めた。ここで、回帰係数から得られる地震規模の評価は従来の震源距離より評価される物より精度が高かった。 (2)国土数値情報を用いた表層地質分類による補正係数 さらに、GISソフトにより観測点と国土数値情報を結びつけることにより、求められた回帰式からの観測震度との差を表層地質により分類した。これより地形分類と震度差が密接な関係があることが明らかになり、各地形分類に対する震度の補正係数を導出した。 (3)他地域への適用 求められた、各地震における回帰式と表層地質による補正係数を用いて、東北地方の震度分布図を予測し、存在する震度分布図と比較したところ、距離減衰式で求められる予測震度よりも精度の高い予測が行えていることが明らかになった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 1998 -1999 
    Author : OKADA Shigeyuki, TAKAI Nobuo
     
    Near field earthquakes bring catastrophic disasters in large urbanized cities. Local governments must prepare the regional mitigation plans on the basis of seismic hazard and risk estimation in order to protect the building environment and the population. In case of Sapporo City, that is our research target, it is difficult to specify the source parameters of near field earthquakes affected the populated area. It is necessary to investigate the influence of indefinite parameters upon the risk assessment. In this paper, we enforced an importance of the plural estimation of seismic damages by probable earthquakes occurring near the urban area. Paying attention to the difficulties of taking measures against all of the cases on estimated damages, we gave an example of the rule of making decision about the priority of mitigation plans from the point of view of earthquake engineering and political science. Finally, we applied the Analytical Hierarchical Approach proposed by T.L.Saaty to decision-making on priority measures for earthquake prevention planning.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 1998 -1999 
    Author : KAGAMI Hiroshi, TAKAI Nobuo
     
    Problems on earthquake disasters in rural area are discussed through the experiences due to recent damaging earthquakes attacked Hokkaido, northern Japan. In the field of earthquake disaster engineering, main concern has been focused on the problems in the densely populated area in large cities. It is obvious that in a large city seismic risk is very high because of concentration of vulnerable structures and complex functions. On the contrary in rural area seismic risk is rather small compared with urbanized area in general but there might be different problems due to the situation of isolation and less population in wide area. From the ratio of area, the chance to be attacked by earthquakes is much higher in rural area than in urbanized area. Therefore the problems in the rural area is also important in the earthquake disaster mitigation programs. In Hokkaido, northern most Japan, we had three large damaging earthquakes in 1993 and 1994. These events attacked not only urbanized area but also more wide rural area and caused much damages in primary industrial area. In this paper, problems on earthquake disasters are discussed through the experiences of three earthquakes. Firstly, reconnaissance reports, various data in local government and organizations, newspapers and related statistics are gathered and rearranged. Secondary, damaging and recovery processes and their effects to local society are revealed for each sector and specified problems in rural area are pointed out. Finally, new approach to the disaster mitigation programs in rural area is indicated.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Exploratory Research
    Date (from‐to) : 1997 -1999 
    Author : 岡田 成幸, 高井 伸雄
     
    本研究は地震による建物破壊に起因する人的被害の抜本的低減を目的としており、激震下における人的被害を「建物構造破壊」→「建物内部崩壊」→「生存空間被災」→「人的被害発生」という時系列展開に基づくメカニズムで理解するためのアプローチ法を提言するものである。そのために必要なツールとして、建物の力学的崩壊パターンを数量評価する尺度および崩壊家屋内の生存空間の保存状態を記述する尺度構成を議論する。 本研究は3ヵ年の研究期間を予定しており、遅滞なく進めるために以下のサブテーマを想定した。 (1)サブテーマ1 : 基礎資料の構築 (2)サブテーマ2 : 建物内生存空間の崩壊パターン記述法の考察 (3)サブテーマ3 : 構造被害-生存空間被害-死傷者の関係考察 (4)サブテーマ4 : 死傷者発生モデルの検討 平成11年度は最終年度に当たる。初年度はサブテーマ1の研究遂行のためのデータベース化が主作業であった。2年度はそのデータに基づいた、建物崩壊パターン記述法(サブテーマ2)及び建物被害パターンと建物内人的被害との関係考察(サブテーマ3)のためのデータ収集に力点が置かれた。本年度の成果は、建物崩壊パターン記述法に関し、2年度において得られた木造建物被害パターンに加え、鉄筋コンクリート構造に関する被害パターン分類をトルココジャエリ地震(1999年)の被害写真より20分類し、それぞれのパターンごとに死者発生率を算定した。さらに、阪神淡路大震災の神戸市における航空写真を立体視解析し、人的被害データとコンバインすることにより、木造被害20分類についても、それぞれの死者発生率を求めることが出来た。この結果、従来の被害4分類より推定される死者予測式に比し、格段に精度・信頼度の高い推定式を構成することが出来た。 また、本研究で提示した分類及び関数は本研究目的以外にも被害調査に一般的に利用できることなどが確認され、研究の副産物として十分意義深いものと位置づけられる。成果の一部は学会誌に投稿した。
  • 伝統的町並みにおける景観保全と地震時安全性の共存に関する研究
    セコム科学技術振興財団：
    Date (from‐to) : 1998 -1998 
    Author : 高井 伸雄
  • 都市形成史を考慮した地域地震危険度評価に関する研究
    日本学術振興会：科学研究費補助金 特別研究員奨励費
    Date (from‐to) : 1996 -1996 
    Author : 高井 伸雄

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