2019年吉林宁江MS5.1地震全矩张量反演及其发震机理初探

Full Moment Tensor Inversion for the 2019 Ningjiang MS5.1 Earthquake in Jilin Province and Study on Its Seismogenic Mechanism

摘要:

采用吉林、黑龙江、辽宁和内蒙古地震台网记录的地震波形数据，利用ISOLA近震全波形反演方法对2019年5月18日吉林宁江M_S5.1地震进行全矩张量反演。结果表明，该地震的最佳断层面解节面Ⅰ走向304°/倾角81°/滑动角26°，节面Ⅱ走向210°/倾角65°/滑动角170°；最佳矩心深度6km，矩震级M_W5.0。根据宁江M_S5.1地震序列展布形态，推断节面Ⅱ可能为优势发震断层面，即本次地震的主控断裂为扶余-肇东断裂，和与其正交的第二松花江断裂共同控制着余震展布方向。全矩张量解在Husdon震源类型图上的投影显示本次地震具有明显的非双力偶成分，是1次体积增加的张性破裂。根据区域地质构造特征和震源区接收函数、电磁测深和地下热结构等地球物理研究结果，综合分析认为在西太平洋板块作用形成俯冲带的同时，也相应地产生了热物质上涌，这些地球物理过程可能会改变莫霍面形态，使其向上突起并作用于活动断层，从而形成此次吉林宁江M_S5.1地震。

Abstract:

In this paper,the full moment tensor solution of M_S5.1 earthquake in Ningjiang,Jilin on May 18,2019 is extracted from the regional waveforms recorded by the Digital Seismic Networks of Jilin,Heilongjiang,Liaoning,and Inner Mongolia Autonomous Region with ISOLA program package. The focal mechanism solutions(nodal plane Ⅰ:strike=304°/dip=81°/rake=26°,nodal plane Ⅱ:strike=210°/dip=65°/rake=170°) of the Ningjiang earthquake show that the earthquake occurred as a result of strike-slip faulting at the shallow centroid depth of 6km with M_W5.0. The Husdon diagram shows the earthquake has an obvious non-DC component with volume expanding. Combining with the regional geological tectonic setting and a number of previous achievements in the source areas from the receiver function,electromagnetic sounding,and underground thermal structure,we infer that the geophysical process of the thermal fluids caused by the subduction of the western Pacific plate might change the Moho formation,which acts on the active faults to generate the M_S5.1 earthquake in the Ningjiang area.