Double-difference relocation of earthquakes in central-western China, 1992-1999

The double-difference earthquake location algorithm was applied to the relocation of 10,057 earthquakes that occurred in central-western China (21 degrees N to 36 degrees N, 98 degrees E to 111 degrees E) during the period from 1992 to 1999. In total, 79,706 readings for P waves and 72,169 readings for S waves were used in the relocation. The relocated seismicity (6,496 earthquakes) images fault structures at seismogenic depths that are in close correlation with the tectonic structure of major fault systems expressed at the surface. The new focal depths confirm that most earthquakes (91%) in this region occur at depths less than 20 km.