Dynamic rupture process of the 2018 Hokkaido Mw6.6 earthquake, Japan

The Mw6.6 earthquake occurred in the Higashi-Geizen area of Hokkaido, Japan, on September 5, 2018, at a depth of 37 km, which exceeds the depth of the brittle-ductile boundary between the crust and the upper mantle and produces strong damage at the surface. In order to study the seismic tectonics of the source region of the Hokkaido earthquake and the physical mechanism that generates strong ground motions, this paper investigated the dynamics of this earthquake, and attempts to invert the dynamic rupture process based on a kinematic source model. First, the kinematic model of the Hokkaido earthquake was used to analyze and calculate the shear stresses on the fault plane, and it was found that the rupture process basically followed the slip-weakening friction law. Based on this result, an initial dynamic source model was built. Then the dynamic rupture process of the earthquake was inverted by the trial-and-error method. Our results show that the dynamic source rupture process of the Hokkaido earthquake was dominated by strike-slip in the rupture initiating area, and at first propagated toward NE and then toward SW. Finally propagated toward the up-dip direction of the fault plane, producing thrust rupture at the bend of the fault. At the location of thrust rupture, the slip rate and total slip reach their maximum values. Combined with the analysis of kinematic and dynamic inversion results, it is inferred that the region is a strong motion generation zone (SMGA). The strong-ground motions generated from the SMGA mainly caused this earthquake disaster.