断-块模型中走滑型地震应力触发研究--以青藏高原北部几次强震为例

Stress triggering of strike-slip earthquakes in fault-block models—A case of several strong earthquakes in Northern Qinghai-Xizang Plateau

从发震断层与活动块体的分布关系出发,以青藏高原北部地区几次强震为例,研究了介质非连续的断—块构造模型中地震永久位移造成的区域断层静库仑应力变化.研究表明,在断块构造模型中,走滑型为主的地震位错引起的区域断层库仑应力变化在地震破裂面以外随距离衰减很快,影响范围仅为几十公里,和余震分布尺度相当;对有地表破裂数据的1 937年M7.5花石峡地震、1997年M7.5玛尼地震和2001年M7.8可可西里地震的模拟结果显示,先前地震的断层位移在后续地震断层面所造成的库仑应力甚微,预示了远距离地震之间的静应力触发效应不明显.

Based on the relationships between active blocks and the surrounding faults, we studied the static Coulomb failure stress（CFS） changes due to eoseismic dislocation of several strong earthquakes in northern Tibetan area using a 3-D model characterized by discontinuous structure in order to simulate the possible tectonic condition existing between blocks and faults. The results indicate that the CFS changes due to strike-slip displacement attenuate rapidly along with the extension of distance away from the focus and the scale of distinct CFS changes is about tens of kilometers, which is similar to the distribution of aftershoeks. Simulation results of the 1937 MT. 5 Huashixia, 1997 M7. 5 Mani, and 2001 MT. 8 Hoh Xil earthquakes for which measured data of dislocations are available, indicate that CFS changes produced by the earlier shock at the later locus are so small that the effect of stress triggering between earthquakes of long distance is not so distinct.