1969年阳江6.4级地震成因的讨论

本文根据阳江地震发生的情况、震源区地质背景、外因的调制作用,对阳江6.4级地震成因进行了讨论。文中提出地震沿着北东东向断层发生,主要作走滑错动,在南偏西的方向上有较强的纵波发射。区域构造应力方向为南东东方向,同时迭加有震源底部垂直作用力。文中分析了震区地质背景,指出地震应力积累单元长约40公里,地震发生后,断层上盘发生陷落,造成震中区地面下沉、余震机制倾滑分量增大等现象。

DISCUSSION ON THE GENESIS OF M=6.4 YANGJIANG EARTHQUAKE IN 1969

This paper deals with the seismic genesis of M=6.3 Yangjiang earthquake in 1969 bymeans of the situation when the quake occurred, its focus geological background and epigene adjustment action.This earthquake mentioned in the paper occurred along NEE fault, with strike slip fault shifting and stronger P wave emission in the direction of S by W. But then the regional tectonic pressure acted upon the fault was of the SEE trending, and at the same time, it was overlapped by a vertical force exerted upon the seismic focus bottom.This paper analyses the geological background in the seismic area and points out that the seismic stress accumulative unit length was 40 km and the focus was formed by the forces mentioned above.M=6.4 earthquake was generated owing to the focus stress accumulation and focus modulation by epigene adjustment action. After earthquake, the fault upper wall was down-punched, resulting in the submergence of ground in the epicentral area and increase of inclined slip component of aftershock meshanism.