Modeling of the Subsurface Structure from the Seismic Bedrock to the Ground Surface for a Broadband Strong Motion Evaluation in Kumamoto Plain
Shigeki Senna*,, Atsushi Wakai*, Haruhiko Suzuki**, Atsushi Yatagai**, Hisanori Matsuyama**, and Hiroyuki Fujiwara*
*National Research Institute for Earth Science and Disaster Resilience
3-1 Tennodai, Tsukuba, Ibaraki 305-0006, Japan
**OYO Corporation, Ibaraki, Japan
During the 2016 Kumamoto earthquakes, two earthquakes of seismic intensity 7 were observed in Mashiki Town, the foreshock (MJMA 6.5) of April 14 and the main shock (MJMA 7.3) of April 16, resulting in significant damage to structures near the fault. The distribution of damage of houses and other buildings  showed a tendency in which damage was concentrated in areas near the surface earthquake fault where the main shock presumably occurred. However, there were locations with slight damage even though they were immediately above the fault and locations with a relatively significant damage even though they were far from the fault. These phenomena are highly likely to be a result of soil structure. First, we built an initial geologic model by collecting boring data in areas of the Kumamoto plain near the fault where damage was severe. Next, we observed microtremors, collected earthquake observational records, and adjusted the layer thickness and S-wave velocity of the initial geologic model. Finally, we built a shallow and deep integrated ground model, compared it to the building damage distribution, and discussed the implications.
-  N. Monma, et al., “Relation between Japanese intensity factor and building damage in Mashiki town due to the 2016 Kumamoto earthquake,” Proc. of JAEE Annual Meeting, O1-2, 2016 (in Japanese).
-  S. Senna, A. Wakai, K. Jin, T. Maeda, K. Kimura, H. Matsuyama, and H. Fujiwara, “Modeling of the subsurface structure from the seismic bedrock to the ground surface for a broadband strong motion evaluation in Kanto area,” JpGU2016 SSS25-12, 2016.
-  Kyushu Branch of Japanese Geotechnical Society, “Kyushu geotechnical information shared database,” 1st edition, 2005 (in Japanese).
-  Kyushu Branch of Japanese Geotechnical Society, “Kyushu geotechnical information shared database,” 2nd edition, 2013 (in Japanese).
-  Kumamoto Geological Survey Association, “Geotechnical engineering map around Kumamoto city,” 2003 (in Japanese).
-  Kumamoto Geological Survey Association, “Urgent open website on boring log for reconstruction assistance from the 2016 Kumamoto Earthquake,” 2016 (in Japanese).
-  Hakusan Corporation, Microtremor observation device JU410, https://www.hakusan.co.jp/products/keisoku/ju410.html (in Japanese) [accessed April 1, 2017]
-  I. Cho, S. Senna, and H. Fujiwara, “Miniature array analysis of microtremors,” Geophysics, Vol.78, KS13–KS23, doi:10.1190/geo2012-0248.1, 2013.
-  S. Senna,“A Method for Setting Engineering Bedrock Using Records of Miniature Array Microtremor Observation,” 16th European Conf. on Earthquake Engineering, No.678, 2018.
-  I. Cho and S. Senna, “Constructing a system to explore shallow velocity structures using a miniature microtremor array – Accumulating and utilizing large microtremor datasets –,” Synthesiology, Vol.9, No.2, pp. 86-96, 2016.
-  T. Satoh, C. J. Poran, K. Yamagata, and J. A. Rodriguez, “Soil profiling by spectral analysis of surface waves,” Proc. 2nd Int. Conf. on Recent Advances in Geotechnical Earth-quake Engineering and Soil Dynamics, Vol.2, pp. 1429-1434, 1991.
-  P. C. Pelekis and G. A. Athanasopoulos, “An overview of surface wave methods and a reliabil-ity study of a simplified inversion technique,” Soil Dyn. Earthquake Eng., Vol.31, pp. 1654-1668, 2011.
-  H. Arai and K. Tokimatsu, “S-Wave velocity pro-filing by inversion of microtremor H/V Spectrum,” Bull. Seismol. Soc. Am., Vol.94, pp. 53-63, 2004.
-  H. Yamanaka and H. Ishida, “Application of genetic algorithms to an inversion of surface-wave dispersion data,” Bulletin of the Seismological Society of America, Vol.86, No.2, pp. 436-444, 1996.
-  K. Watanabe, “Geology in the western area of Aso Caldera,” Bulletin of Facalty of Education, Kumamoto University, 1972.
-  K. Wakamatsu and M. Matsuoka, “Development a Geomorphologic-based 7.5-second Site-condition Map for Nationwide Hazard Zon-ings,” Bulletin of Institute of Science and Technology, Kanto Gakuin University, No.40, pp. 31-42, 2012.
-  N. A. C. Cressie, “Statistics for Spatial Data,” John Wiley and Sons Inc., New York, p. 928, 1993.
-  M. Yoshimi et al., “Borehole exploration in heavily damaged area of the 2016 Kumamoto Earthquake, Mashiki town, Kumamoto,” JSAF Annual Meeting Proc., 2016 (in Japanese).
-  City Bureau of MLIT, “Interim report on safety measures for the urban area reconstruction in Mashiki town from the 2016 Kumamoto earthquake,” Dec. 22, 2016 (in Japanese).
-  Y. Shirahama, et al, “Characteristics of the sur-face ruptures associated with the 2016 Kumamoto earthquake sequence,” Central Kyushu, Japan, Earth Planets Space, Vol.68, No.191, doi:10.1186/s40623-016-0559-1, 2016.
-  S. Kataoka et al., “Attnuation relationships of ground motion intensity using short period level as variable,” J. JSCE A, Vol.62, No.4, pp. 740-757, 2006 (in Japanese).
-  A. Nozu and T. Nagao, “Site amplification factors for strong-motion sites in JAPAN based on spectral inversion technique,” Technical note of the port and airport presearch institute, Vol.1112, p. 56, 2005 (in Japanese).
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