Seismological evidence of ultra-crust faults in northeastern margin of Qinghai-Tibet Plateau

The crustal structure beneath the temporary seismic array is imaged with teleseismic receiver functions in Tianshui earthquake-prone area in the northeast margin of Qinghai-Tibet Plateau. The results indicate that the Lueyang-Diebu fault and the north margin of West Qinling Mountains fault are ultra-crust faults which penetrate the Moho and lead to the weakness of impendence-contrast of Moho. The earthquakes in this area often nucleate in the margin region with sharp variety of the velocity, and the huge earthquakes in history might occurred near the asperity resulting from the interaction between faults and Conrad discontinuity at the depth of about 20 km .