Upper crustal velocity and seismogenic environment of the <em>M</em>7.0 Jiuzhaigou earthquake region in Sichuan, China

Abstract

The P-wave velocity structure of the upper crust around the Jiuzhaigou earthquake region shows obvious lateral inhomogeneity, lowvelocity anomalies are observed at the intersection of shallow part of Minjiang and Tazang faults. qThe relocated earthquake sequence distributed along the NW-SE direction and ends near the intersection of the Minjiang and Tazang faults, the inhomogeneous variation of the velocity structure of the Jiuzhaigou earthquake region and its surrounding medium is the deep structural factor controlling the spatial distribution of the mainshock and its sequence. qThe crustal low-velocity layer of northeastern Songpan-Garzê Block stretches into Minshan Mountain, and migrates to the northeast, the tendency to emerge as a shallow layer is impeded by the high velocity zone of Nanping Nappe tectonics and Bikou Block.