開発機械/岩盤工学/資源開発技術

[3K62501-09-03] Estimating the earthquake source mechanism using full waveform inversion

○Iktae JANG¹, Hitoshi Mikada¹, Junichi Takekawa¹ (1. Kyoto University)

Keywords:full waveform inversion, earthquake source mechanism, numerical experiment

For realization of the safe society from an earthquake, an early warning system which is necessary to obtain the accurate data issued to the public has been widely introduced in earthquake prone countries such as Japan and America. One of the most important tasks for considering the accuracy and the promptness of information when an earthquake occurs is estimating the earthquake source mechanism. Many recent studies have proposed methods for estimating physical mechanism of earthquake source and the centroid-moment tensor (CMT) solution that represents the stress tensor centered at the hypocenter at the occurrence moment could be one alternative. However, it is required to consider the location of a fault plane and the time sequence of fault propagation which means we need to refer to spatial distribution of aftershocks for the determination of the fault plane among two nodal planes.

Since contribution of quick estimation of focal mechanism to disaster mitigation is obvious, developing the method for estimating focal mechanism immediately has become an important task. To solve this problem, Cordrie and Mikada (2017) proposed a novel way which uses full waveforms for the estimation. Full-waveform inversion (FWI) has recently been proposed to estimate high resolution seismic velocity model (Tarantola, 1986), however, it has not been investigated the applicability of estimating fault parameters using inversion method yet.

In view of this point, we consider developing the estimation method of earthquake source parameters using FWI and as a first step in this study, we investigate the applicability of FWI evaluating three fault parameters (strike, dip and rake) assuming a known source time function. The numerical results indicate that FWI can estimate the fault parameters without long time observation.