2019年10月2日贵州沿河MS4.9地震震害特征及发震构造分析

贵州沿河M_S4.9地震发生在历史地震强度较低的上扬子地块凤冈SN向隔槽式褶皱变形区。通过地震地质背景分析、震害调查、震源机制解、断层调查和库区水位变化情况等,得到主要认识如下:由于震源深度浅、灾区老旧自建房抗震性能差,导致本次地震直接经济损失严重;本次地震主震的机制解为节面Ⅰ:走向61°/倾角35°/滑动角135°,节面Ⅱ:走向190°/倾角66°/滑动角63°,表现为走向NE、逆冲兼平移型运动方式;结合等震线走向及震中主要断层性质,判断NE向沿河断层为本次地震主震的发震构造,并进一步推测此次地震为水库诱发断层活化引起的地震。

Analysis of Earthquake Damage Characteristics and Seismogenic Structure of Yanhe MS4.9 Earthquake in Guizhou Province on October 2,2019

The Yanhe M_S4.9 earthquake occurred in the north-south direction of Fenggang fold deformation area of the upper Yangtze block,where very few earthquakes had been recorded in the past. Through seismic geological background analysis,earthquake damage investigation,focal mechanism solution,fault investigation and water level change in the reservoir area,we obtained the main understandings as follows. Due to the shallow focal depth and poor seismic performance of old self built houses in the disaster area,the direct economic losses of the earthquake were serious. The focal mechanism of the Yanhe earthquake is as that:nodal plane I was strike=61°,dip=35°,rake=135°,and nodal plane II was strike=190°,dip=66°,rake=63°,which suggests a NE strike,thrust and translation. Combined with the trend of isoseismal line and the properties of main faults at the epicenter,we believe that the NE Yanhe Fault is the seismogenic structure of the main earthquake of this earthquake. it is further inferred that the earthquake was caused by reservoir induced fault activation.