Strong Motion Simulation of the Hypothetical M7 Intraplate Earthquake beneath Tokyo Metropolitan Area Using MeSO-net Observation Data

Abstract

Recently, an M7-class earthquake within the Philippine Sea plate has been highlighted as the most disastrous earthquake for the Tokyo metropolitan area. We performed broad-band strong motion simulation of such an earthquake by the empirical Green's function (EGF) method using the strong motion records obtained by MeSO-net, which has been deployed in Kanto region at minimum interval of 2 km. Our fault models corresponded to the two nodal planes of the EGF event with one strong motion generation area whose parameters followed the fault model used in the strong motion evaluation by Cabinet Office (2013). The strong motion generation area was divided into subfaults having the EGF event size estimated by the waveform modeling of the EGF event. The rupture propagation directions were assumed toward the Tokyo metropolitan area. MeSO-net stations have accelerometer at 20 m depth, therefore, the seismic intensities on the surface were estimated using the temporal observation data on the surface. A comparison of the acceleration response spectra between the two fault models shows that the response around 1 s amplified for the stations located in the rupture propagation direction. The seismic intensity distribution shows that there are more stations recording large seismic intensities in the rupture propagation directions than around the source areas. For such stations, particularly located around the western Tokyo prefecture, larger seismic intensity was also observed for the EGF event. The distinctive seismic intensity distribution derived in this study was reproduced by the strong motion characteristics included in the EGF event and rupture directivity effect.