[S21-P] Poster

[S21-P-15] Heterogeneous structure beneath fault zones of the 2016 Kumamoto earthquake

^○Megumi Kamizono¹, Satoshi Matsumoto¹, Yusuke Yamashita², Manami Nakamoto³, Masahiro Miyazaki², Shin-ichi Sakai⁴, Yoshihisa Iio², Group for urgent joint seismic observation of the 2016 Kumamoto earthquake¹ (1.Kyushu University, Fukuoka, Japan, 2.Kyoto University, Kyoto, Japan, 3.National Institute of Polar Research,Tokyo, Japan, 4.The University of Tokyo, Tokyo, Japan)

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 mechanism of this earthquake has a tension axis approximately in the north-south direction and strike-slip fault type. Furthermore, in the Beppu-Haneyama fault zone, located in northeastern part of Kumamoto, induced earthquake (M5.7; reference value) occurred at 01:25 (JST) on April 16th. In this area, there are mainly two active fault zones which are the Futagawa fault zone and Hinagu fault zone. Aso volcano exists in the northeastern part of Kumamoto prefecture, the end of the Futagawa fault zone and it erupted after main shock. The 2016 Kumamoto earthquake is characterized in that the range of seismic activity is very wide and vigorous aftershock activity.
Because the network of seismic stations (58 offline and 13 online seismic observation points) were deployed by Group for urgent joint seismic observation of the 2016 Kumamoto earthquake from April 15, many data of active seismicity were obtained.
We analyzed data of aftershock of the 2016 Kumamoto earthquake. We estimated background structure by comparing the observed envelope with theoretical curve based on multiple scattering model. As a result, there are heterogeneity in the western part of the Hinagu fault zone and beneath the Aso volcano.
As a future task, by comparing the observed envelope with the theoretically expected curve we will estimate the distribution of scatterers based on travel time of the ripples.