[S-CG43] Shallow and intermediate depth intraslab earthquakes: seismogenesis and rheology of the slab

[SCG43-04] Estimate the Physical Implication of the Faulting Process of the Intra-Slab Earthquake based on the Finite-Fault Source Inversion

*Kenichi Tsuda¹, Shohei Yoshida², Chen Ji⁴, Ralph J Archuleta^3,4, Toshiaki Sato² (1.Institute of Technology, Shimizu Corporation, 2.Ohsaki Research Institute Inc., 3.RJA Ground Motion Analysis, Inc,, 4.University of California Santa Barbara)

Keywords:Finite Fault Inversion, Intraslab Earthquake, 2022 Hyuganada Earthquake, 2021 Fukushima-Oki Earthquake

Determining the parameters of the rupture process of large earthquakes is essential to understanding the physics of the faulting process. These parameters are critical in mitigating the seismic hazard from future events. It is now common to generate dislocation faulting models immediately after the occurrence of a large earthquake. These models are derived from a variety of data: seismic waveforms, both regional and the far-field data; GPS and InSar geodetic data; and geological field data. These models are dependent on the assumptions: the physical description of the fault plane(s), slip-rate functions, range of rupture velocity, etc. Inversion of data to determine the faulting process of the earthquakes occurring in similar tectonic settings but on different tectonic regions can delineate how various tectonic parameters, such as plate age, convergence rate, and slab curvature, affect the physics of the rupture process.
To investigate such differences, we have compared the faulting process of the intraslab earthquake on different plates. We used the finite-fault source inversion (Ji et al., 2002) to develop a source model for the 2022 Hyuganada earthquake (Mw 6.4) that occurred on the January 22, within the Philippine-Sea Plate. The frequency range used for the inversion is 0.1-1.0 Hz. The area with large slip is compact, occurring around the hypocenter (maximum slip is around 1.3m). The stress drop is about 9 MPa (Noda et al., 2013). We show the slip distribution and moment-rate function in Figures (a) & (b), respectively. We compared this result with the intraslab earthquakes on the Pacific plate, including 2021 Fukushima-Oki earthquake which had higher stress drop compared to this Hyuganada earthquake (Tsuda et al., 2022). Both are intraplate earthquakes occurring near the plate interface, Hyuganada earthquake reflects the downdip extension along the subducted Philippine-Sea slab while Fukushima-Oki earthquake is the result of downdip compression along the subducted Pacific slab. These differences lead to better understanding of the mechanisms that generate ground motion from different plates near Japan.