Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen- tral-western China∗

A simultaneous inversion of earthquake relocation and three-dimensional crustal structure of P-wave velocity in central-western China (21°N~36°N, 98°E~112°E) were performed in this paper. The crustal P-wave velocity model and earthquake relocation for this region are obtained using Pg and Sg phase readings of 9 988 earthquakes from 1992 to 1999 recorded at 193 seismic stations within central-western China by SPHYPIT90 and SPHREL3D90 programs. A lateral inhomogeneous structure of P-wave velocity in this region was obtained. Ob-vious contrast of P-wave velocities was revealed on both sides of active fault zones. Relocated epicenters of 6 459 events show clear lineation along active faults, which indicated a close correlation between seismicity and the active faults in this region. Focal depths of 82 % relocated events ranged from 0 to 20 km, which is in good agreement with that from double-difference earthquake location algorithm. Key words: simultaneous inversion; 3-D P-wave velocity structure; earthquake relocation; central-western Chin