Tao Gou, Zhouchuan Huang, Dapeng Zhao, Liangshu Wang
Journal of Geophysical Research: Solid Earth
We investigate 3-D seismic structures(Vp, Vs and Poisson's ration) and Vp azimuthal anisotropy in the source area of the 2018 Eastern lburi earthquake(M6.7) in Hokkaido, Japan. Its mainshock occurred at the edge of a high-Vp(2 - 4%) seismogenic zone. Significant low-Vs (-1 to 3%) and high Poisson's ration (2-7%) anomalies are imaged in and below the source zone and extend to the upper surface of the subducting Pacific slab, most likely reflecting ascending fluids released by the slab dehydration. A high consistency between the fault plane and the low-Vs and high Poisson's ration anomalies indicates that the fluids may have entered the fault and affected the rupture nucleation. A high-V (1-3%) anomaly is revealed in the force-arc mantle wedge and connects with the high-V seismogeniz zone, probably reflecting a lithospheric fragment and contributing to around the soucre area, which may reflect complicated stress regime and strong structural heterogeneities here.