Japan Geoscience Union Meeting 2018

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[EJ] Oral

S (Solid Earth Sciences) » S-SS Seismology

[S-SS10] Seismic wave propagation: Theory and Application

Thu. May 24, 2018 9:00 AM - 10:30 AM A10 (Tokyo Bay Makuhari Hall)

convener:Kiwamu Nishida(Earthquake Research Institute, University of Tokyo), Kazuya Shiraishi(Japan Agency for Marine-Earth Science and Technology), Takao Nibe(（株）地球科学総合研究所, 共同), Kaoru Sawazaki(National Research Institute for Earth Science and Disaster Resilience), Chairperson:Emoto Kentaro(東北大学), Takahashi Tsutomu(JAMSTEC)

10:00 AM - 10:15 AM

[SSS10-11] The seismic attenuation structure in the focal area of the 2016 Kumamoto earthquake

*Megumi Kamizono1, Satoshi Matsumoto2, Azusa Shito2, Yusuke Yamashita3, Manami Nakamoto4, Masahiro Miyazaki3, Shin'ichi Sakai5, Yoshihisa Iio3, Group for urgent joint seismic observation of the 2016 Kumamoto earthquake (1.Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, 2.Institute of Seismology and Volcanology, Faculty of Science, Kyushu University, 3.Disaster Prevention Research Institute, Kyoto University, 4.National Institute of Polar Research, 5.Earthquake Research Institute, University of Tokyo)

Keywords:The 2016 Kumamoto earthquake, seismic attenuation, Futagawa - Hinagu fault zone

The 2016 Kumamoto earthquake occurred in April 2016. The first earthquake (M6.5) occurred at 21:26 (JST) on April 14th. The main shock (M7.3) occurred at 1:25 (JST) on April 16th. The aftershock activity is high and the active area covers entire Hinagu and Futagawa fault zones. The velocity structure by travel time tomography method in this area suggested that the heterogeneous feature controlled the seismic activity. In this study, we investigate relationship between the activity and heterogeneous structure with shorter wavelength.
Small scale heterogeneity in the earth is evaluated from attenuation factors of seismic waves as Q-1 value. We analyzed data before and after the 2016 Kumamoto earthquake and estimated the Q-1 values for both intrinsic and scattering attenuation. To estimate spatial distribution of the attenuation factors, Del Pezzo et al. (2016) had proposed a method in which the spatial weighting functions for estimated Q-1 values of many source-receiver pairs was adopted. However, the weighting function was not applicable to our data because of various hypocentral distance until several tens kilometers. Therefore, in this study, we consider the appropriate weighting function by Monte-Carlo simulation and estimate the Q-1 structure in the hypocentral area of the 2016 Kumamoto earthquake.


Acknowledgements
We used data by JMA, NIED, Kyoto and Kyushu Universities. We are grateful to Dr. Hoshiba for the computation program of Monte-Carlo simulation.