利用Virtual Quake地震模拟器研究鲜水河断裂带地震活动性与地震复发周期

Seismicity and Earthquake Recurrence Period along the Xianshuihe Fault with Virtual Quake Earthquake Simulator

摘要:

2022年9月5日四川泸定6.8级地震发生在鲜水河断裂带磨西断裂上。本文依据鲜水河断裂带的断层几何形态、断层面物理力学参数、断层滑移速率等基础资料,构建断裂带三维模型,基于Virtual Quake 地震模拟器开展鲜水河断裂带准静态数值模拟。对七条分支断裂独立模拟的结果显示模拟结果与历史地震的最大震级和复发周期具有较好的一致性。结果表明模型长度影响震级大小,滑移速率影响地震复发周期。断层面几何弯曲展布使得断层面应力分布不均匀,在弯曲处出现应力积累的现象,易触发地震,并出现了地震分段破裂现象,降低了几何弯曲断层的地震频次,为强震的孕育创造了条件。联合模拟的10000年时间内,鲜水河断裂带共发生了33次M≥7.0地震,最大震级为M7.6,地震活动性呈现一定的活跃期与平静期。断层系统地震间的相互应力作用和复杂的断层几何结构影响着地震迁移的复杂性。道孚断裂上相距40年发生两次M≥7.0地震,乾宁断裂北端相距5.8年发生M≥7.0双震,此类现象与历史地震有一定的相似性。

Abstract:

The Luding M_S6.8 earthquake occurred on Moxi Fault of the Xianshuihe fault zone on September 5,2022. In this paper we built a three-dimensional model of the Xianshuihe fault based on fault geometry,physical and mechanical fault parameters and fault slip rate. Using Virtual Quake earthquake simulator,we conducted massive calculation to carry out the Xianshuihe fault quasi-static numerical simulation. The independent simulations results of seven branch faults of the Xianshuihe fault are found to be in conformance with the biggest historical earthquakes and earthquake recurrence cycles. We found that bending of fault plane may result in uniform stress distribution,and the stress may accumulate at the bend location,where is easy to trigger earthquakes. The rupture segmentation reduces the seismic frequency and creates conditions for strong earthquakes. During the 10000 years of united simulation along the Xianshuihe fault,there are 33 M≥7.0 earthquakes with the biggest one of M7.6. The interaction among the earthquakes in the fault system and the complicated fault geometry influence the earthquake migration. The simulation results of two M≥7.0 earthquakes along the Daofu fault within 40 years and two M≥7.0 earthquakes along the north part of the Qianning fault within 5.8 years is consistent to historical earthquake records.