广西北流-广东化州MS5.2级地震发震构造探讨

Discussion on the Seismogenic Structure of the Beiliu-Huazhou MS 5.2 Earthquake in the Junction of Guangxi and Guangdong

2019年10月12日广西北流与广东化州交界发生5.2级地震,地震发生前2 s,其北西侧发生4.2级前震。根据地震周边47个台站记录到的P波及S波震相走时数据,利用双差地震定位方法获取了104个地震的精定位结果,结合4.2级前震的震源机制解及5.2级主震的“中心震源机制解”进行研究探讨,综合分析认为NW-SE向米场-石窝断裂可能是北流4.2级前震和5.2级主震的主要发震构造,前震孕震过程有NEESWW向茶山断裂的参与。而5.2级主震位于米场-石窝断裂与NE-SW向信宜-廉江断裂交汇处,该交汇处应力薄弱且距离前震仅1km左右,推测4.2级前震的发生可能对5.2级地震具有触发作用,5.2级地震发生后余震主要沿米场-石窝断裂的延伸线分布。

The MS5.2 earthquake occurred at the junction of Huazhou city of Guangdong province and Beiliu city of Guangxi province.There is a ML4.2 earthquake occurred 2 sec before the MS5.2 earthquake.This paper obtains 135 relocated earthquakes by applying Double-Difference seismiTc location method and the focal mechanism of the foreshock and mainshock.The research suggests that Michang-Shiwo fault with NW-SE trending might be the main seismogenic structure of the foreshock and mainshock.Additional,the Chashan fault with NEE-SWW trending involves the pregnant process of the ML4.2 foreshock.The MS5.2 mainshocklocates at the intersection of Michang-Shiwo fault and Xinyi-Lianjiang fault,while the intersection is only about 1km from the foreshock,which suggests that the ML4.2 foreshock might trigger the MS5.2 mainshock.Finally,the aftershock sequence distributes along the extension line of the Michang-Shiwo fault.