Modeling of Subsurface Velocity Structures from Seismic Bedrock to Ground Surface in the Tokai Region, Japan, for Broadband Strong Ground Motion Prediction
Atsushi Wakai*,, Shigeki Senna*, Kaoru Jin**, Atsushi Yatagai**, Haruhiko Suzuki**, Yoshiaki Inagaki**, Hisanori Matsuyama**, and Hiroyuki Fujiwara*
*National Research Institute for Earth Science and Disaster Resilience (NIED)
3-1 Tennodai, Tsukuba, Ibaraki 305-0006, Japan
**OYO Corporation, Tsukuba, Japan
For sophistication of strong ground motion prediction in terms of disaster mitigation, one of the principal issues is to model subsurface velocity structures so that characteristics of earthquake ground motions can be reproduced in the broadband range 0.1 Hz to 10 Hz. In recent years, subsurface structures have been modeled in sedimentary layers on seismic bedrock for a few regions of Japan, in a national project. In this study, subsurface velocity structures were modeled from seismic bedrock to the ground surface for the Tokai region. These models were constructed in accordance with the subsurface velocity structure modeling scheme published by the Headquarters for Earthquake Research Promotion. To begin with, initial models were constructed based on existing bore-hole data, geological information, etc. Next, they were improved based on results of microtremor explorations which had been conducted in recent years. It was found that the new model had different characteristics to the conventional model. This paper will present the modeling process and characteristics of distribution maps for velocity structures and amplification index.
-  Cabinet office, Government of Japan, “Damage estimate on Nankai Trough megathrust earthquake (the initial report),” http://www.bousai.go.jp/jishin/nankai/taisaku/pdf/20120829_higai.pdf (in Japanese) [accessed June 18, 2019]
-  The Headquarters for Earthquake Research Promotion, “Modeling concept of subsurface structures from seismic bedrock to ground surface,” https://www.jishin.go.jp/evaluation/seismic_hazard_map/underground_model/ (in Japanese) [accessed February 8, 2019]
-  S. Senna, T. Maeda, Y. Inagaki, H. Suzuki, H Matsuyama, and H. Fujiwara, “Modeling of the subsurface structure from the seismic bedrock to the ground surface for a broadband strong motion evaluation,” J. Disaster Res., Vol.8, No.5, pp. 889-903, 2013.
-  S. Senna, A. Wakai, A. Yatagai, K. Jin, H Matsuyama, H. Suzuki, and H. Fujiwara, “Modeling of the subsurface structure from the seismic bedrock to the ground surface for a broadband strong motion evaluation in Japan,” Proc. of 7th Int. Conf. of Earthquake Geotechnical Engineering, 2019 (in press).
-  S. Senna and H. Fujiwara, “Development of analyzing tools for microtremor survey measurement data, vol.1 – Tools for analysis of microtremor data –,” Technical Note of NIED, No.313, pp. 1-133, 2008 (in Japanese).
-  Hakusan Corporation, “Microtremor Measurement Unit JU410,” https://www.hakusan.co.jp/products/keisoku/ju410.html (in Japanese) [accessed February 8, 2019]
-  I. Cho, S. Senna, and H. Fujiwara, “Miniature array analysis of microtremors,” Geophysics, Vol.78, No.1, pp. KS13-KS23, doi:10.1190/geo2012-0248.1, 2013.
-  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. 87-98, 2016.
-  T. Satoh, K. Yamagata, C. J. Poran, and J. A. Rodriguez, “Soil profiling by spectral analysis of surface waves,” Proc. 2nd Int. Conf. on Recent Advances in Geotechnical Earthquake Engineering & Soil Dynamics, Vol.2, pp. 1429-1434, 1991.
-  P. C. Pelekis and G. A. Athanasopoulos, “An overview of surface wave methods and a reliability study of a simplified inversion technique,” Soil Dyn. Earthquake Eng., Vol.31, No.12, pp. 1654-1668, 2011.
-  K. Aki, “Space and time spectra of stationary stochastic waves, with special reference to microtremors,” Bull. Earthquake Res. Inst., No.35, pp. 415-457, 1957.
-  H. Okada, “The microtremor survey method,” Geophysical Monograph Series No.12, Society of Exploration Geophysics, 2003.
-  H. Yamanaka and H. Ishida, “Phase velocity inversion using genetic algorithms,” J. Struct. Constr. Eng., Vol.60, No.468, pp. 9-17, 1995 (in Japanese).
-  H. Arai and K. Tokimatsu, “S-Wave velocity pro-filing by inversion of microtremor H/V Spectrum,” Bull. Seismol. Soc. Am., Vol.94, No.1, pp. 53-63, 2004.
-  H. Horikawa et al., “A three-dimensional subsurface structure model of the Chukyo area, central Japan,” Annual Report on Active Fault and Paleoearthquake Researches, No.8, pp. 203-245, 2008 (in Japanese).
-  H. Fujiwara et al., “A Study on Subsurface Structure Model for Deep Sedimentary layers of Japan for Strong-motion Evaluation,” Technical Note of NIED, No.337, 2009 (in Japanese).
-  K. Wakamatsu and M. Matsuoka, “Development a geomorphologic-based 7.5-second site-condition map for nationwide hazard zonings,” Bulletin of Institute of Science and Technology, Kanto Gakuin University, No.40, pp. 31-42, 2012.
-  Shizuoka Prefecture, “The 4th-phase earthquake damage estimates investigation in Shizuoka Prefecture (the initial report),” 2013 (in Japanese).
-  Central Disaster Management Council, “Committee for technical investigation on Tokai Earthquake,” 2001 (in Japanese).
-  M. Matsuoka, K. Wakamatsu, K. Fujimoto, and S. Midorikawa, “Average shear-wave velocity mapping using Japan engineering geomorphologic classification map,” J. of Structural Mechanics and Earthquake Engineering, No.794/I-72, pp. 239-251, 2005 (in Japanese).
-  N. Cressie, “Statistics for Spatial Data,” John Wiley & Sons, Inc., 900pp., 1993.
-  K. Fujimoto and S. Midorikawa, “Relationship between Average Shear-Wave Velocity and Site Amplification Inferred from Strong Motion Records at Nearby Station Pairs,” J. of Japan Association for Earthquake Engineering, Vol.6, No.1, pp. 11-22, 2006 (in Japanese).
-  S. Kataoka et al., “Attenuation relationships of ground motion intensity using short period level as a variable,” J. of Japan Society of Civil Engineers A, Vol.62, No.4, pp. 740-757, 2006 (in Japanese).
-  T. Satoh and H. Kawase, “Site responses of sediments,” ZISIN, Second Series, Vol.61, Supplement, pp. S455-S470, 2009 (in Japanese).
-  P. G. Somerville and D. V. Helmberger, “The effect of crustal structure on the attenuation of strong ground motion in eastern north America,” Proc. of 4th U. S. National Conf. on Earthq. Eng., Vol.1, pp. 385-394, 1990.
-  K. Konno and T. Ohmachi, “A smoothing function suitable for estimation of amplification factor of the surface ground from microtremor and its application,” J. of Japan Society of Civil Engineers, No.525/I-33, pp. 247-259, 1995 (in Japanese).
-  H. Yamanaka, M. Ohori, and S. Midorikawa, “Estimation of seamless Vs structure for Kanto basin using site amplification from spectral inversion of earthquake motion records,” Summaries of Technical Papers of Annual Meeting Architectural Institute of Japan, B-2, Structures II, Structural Dynamics Nuclear Power Plants, pp. 47-48, 2009 (in Japanese).
-  Y. Fukushima and S. Midorikawa, “Evaluation of site amplification factors based on average characteristics of frequency dependent Q-1 of sedimentary strata,” J. Struct. Constr. Eng., Vol.59, No.460, pp. 37-46, 1994 (in Japanese).
-  H. Kawase and H. Matsuo, “Separation of source, path, and site effects based on the observed data by K-NET, KiK-net, and JMA strong motion network,” J. of Japan Association for Earthquake Engineering, Vol.4, No.1, pp. 33-52, 2004 (in Japanese).
-  A. Nozu and T. Nagao, “Site amplification factors for strong-motion sites in Japan based on spectral inversion technique,” PARI Technical Note, No.1112, 2005 (in Japanese).
-  J. G. Anderson, “Quantitative measure of the goodness-of-fit of synthetic seismograms,” 13th World Conf. on Earthquake Engineering, Paper No.243, 2004.