青藏高原东北缘超壳断裂的地震学证据

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

摘要: 使用天水流动台阵资料，通过远震接收函数偏移成像研究了位于青藏高原东北缘的天水强震区下方地壳速度结构。结果表明位于该区域的略阳 - 迭部和西秦岭北缘断裂为超壳断裂。即断裂达到地壳底部且穿过了莫霍面，导致莫霍面上下两侧速度跃变降低。结果还表明，该区域中强地震常集中发生于地壳内部速度变化显著区域，该区域历史上的巨大地震可能发生在断裂与 20 km 深度附近康拉德界面相互作用的部位。

Abstract: 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 .