晋北地区中强震前后构造应力场变化特征

Characteristics of Structural Stress Field Variation before and after Moderate to Strong Earthquakes in Northern Shanxi Region

基于1990年1月至2021年12月晋北地区中小地震的P波初动极性数据,采用综合震源机制解法反演晋北地区的综合断层面解。结果显示,震源机制解节面为EW和NE向,与晋北地区主要构造线一致;震源错动类型以正断型为主;主压应力方向为NE-NEE,仰角较大,主张应力方向为NW-SE,仰角近水平,与区域构造应力场方向吻合。综合断层面解中,P轴方位与区域优势方位一致时,晋北地区可能孕育中强地震的发生。

Based on the polarity data of P-wave first motions from moderate to small earthquakes in the northern Shanxi region from January 1990 to December 2021,a comprehensive fault plane solution for small earthquakes in the region is obtained using the focal mechanism inversion method.The results show that the focal mechanism solution exhibits EW and NE dip directions,which are consistent with the major structural trends in the northern Shanxi region.The dominant fault type is normal faulting.The principal stress direction is NE-NEE with a relatively high dip angle,while the maximum stress direction is NW-SE with a nearly horizontal dip angle,which corresponds to the regional tectonic stress field.In the comprehensive fault plane solution for small earthquakes,when the P-axis orientation is consistent with the predominant orientation in the region,it suggests the potential occurrence of moderate to strong earthquakes in the northern Shanxi region.