[S-SS09] 地殻構造

[SSS09-04] Constructing a 3D multi-parameter model of the Nankai Trough

*仲西 理子¹、Qin Yanfang¹、Liu Xin²、藤江 剛¹、汐見 勝彦³、小平 秀一¹、高橋 成実³、中村 武史⁴、富士原 敏也¹ (1.海洋研究開発機構、2.香港大学、3.防災科学技術研究所、4.電力中央研究所)

キーワード：南海トラフ、３Dモデル、マルチパラメータ

To predict strong ground motion, tsunamis, seismic hazards, and determine hypocenters with high-resolution, three-dimensional (3D) seismic velocity models must first be determined. Particularly urgent in the Nankai Trough for disaster prevention. We have updated the 3D P-wave velocity (Vp) model [Nakanishi et al., 2018] by combining newly estimated structure information obtained from recent seismic studies. Seismic S-wave (Vs) and density information of the shallow sediments will greatly enhance not only the accuracy of hypocenter determination but also the reliability of earthquake cycle simulation and strong motion prediction. Since the Vs and density structure information in the sea area was very limited (e.g., Takahashi et al., 2002), we have tried to construct a 3D Vs structure model by using empirical conversion equations from Vp to Vs and density (e.g., Hamilton, 1979, Brocher, 2005, Ludwig et al., 1970) applicable to the Nankai Trough area. In addition, we have also collected Vs structure information estimated from the displacement–pressure ratios of the Rayleigh wave (Tonegawa et al., 2017) and seismic tomography (Yamamoto et al., 2022). Furthermore we have also been estimating the structure using ambient noise differential adjoint tomography (Liu et al., in preparation). Consequently, 3D Vs and density models have been derived based on a newly 3D Vp model constructed by combining Vp information from various research sources. To verify our 3D muti-parameter (Vs and density) model, we compared our Vs model that converted from Vp model with Vs structure information estimated by using various survey data. Additionally, we also calculated synthetic Bouguer gravity anomaly and compare it with observed Bouguer anomaly map shown by AIST. In this study, we will show our current 3D multi-parameter model, and compare it with estimated structure model based on observed geophysical data as some kind of model validation. This study is part of 'Research Project for Disaster Prevention on the great Earthquakes along the Nankai Trough' funded by Ministry of Education, Culture, Sports, Science and Technology, Japan. This work is partly supported by JSPS KAKENHI Grant Number 19H01982.