青藏高原东北部的库仑应力积累演化对大地震发生的影响

EVOLUTION OF CUMULATIVE COULOMB FAILURE STRESS IN NORTHEASTERN QINGHAI-XIZANG (TIBETAN) PLATEAU AND ITS EFFECT ON LARGE EARTHQUAKE OCCURRENCE

假定地震可以模拟为多层弹粘性介质中的位错,考虑大地震(M≥7.0)和GPS数据得出的长期构造加载为形变源,依据多层麦克斯韦弹粘性介质中位错产生的应力变化,计算得到了地震产生的应力变化,给出了青藏高原东北部1920年以来积累库仑破裂应力演化.地震破裂的断层长度、宽度和滑动量根据前人统计公式和野外地质调查得到.研究表明,20次M≥7.0地震中,除1990年共和地震、1952年当雄地震和1976年松潘双震的后一个事件外,17次大地震均发生在库仑破裂应力变化为正的区域,触发率达85%.本研究为中长期地震危险性估计在一定程度上提供了基础数据.

We simulate accumulative Coulomb failure stress change in a layered Maxwell viscoelastic media in the northeastern Qinghai-Xizang （Tibetan） Plateau since 1920. Lithospheric stress/strain evolution is assumed to be driven by dislocations of large earthquakes （M≥7.0） and secular tectonic loading. The earthquake rupture parameters such as the fault rupture length, width, and slip are either adopted from field investigations or estimated from their statistic relationships with the earthquake magnitudes and seismic moments. Our study shows that among 20 large earthquakes （M≥7.0） investigated, 17 occurred in areas where the Coulomb failure stress change is positive, with a triggering rate of 85%. This study provides essential data for the intermediate to long-term likelihood estimation of large earthquakes in the northeast Tibetan Plateau.