大同—阳高震区深部构造背景

利用通过本区的宽角反射／折射剖面资料对大同－阳高震区及邻区地壳上地幔速度结构与构造进行了详细的研究，结果表明，地壳上地幔速度结构与构造在纵向和横向上具有明显的不均一性，浅部基底断裂发育，对应其深部，根据波组特征，壳内界面及速度等值线起伏变化和低速异常体的边界等推测了地壳深断裂带，区内最明显的上地壳低速体位于大同－阳原附近，其南界存在地壳断裂，大同－阳高地震群与该低速异常体和深断裂有关。

DEEP TECTONIC BACKGROUND IN DATONG-YANGGAO EARTHQUAKE AREA

Taking advantage of seismic data obtained from wide angle reflection and refract ion profiles passing through this area,the velocity structures and tectonics of the crust and upper mantle in Datong-Yanggao earthquake province and its surrou nding area have been studied in details.The results show:the crust and upper man tle velocity structures and tectonics obviously present both longitudinal and la teral heterogeneity.A great number of basement faults lie in the shallow crust t o wh ich the deep structures correspond.According to the characteristics of waves gro ups,the interfaces of interior crust and the undulations of the velocity contour as well as the boundaries of the low velocity abnormal blocks,deep crustal faul ts are inferred.The most obvious low velocity block in upper crust lies in the n eighbourhood of Datong-Yangyuan and in its south boundary exists deep crustal f ault.Datong-Yanggao earthquake swarm is related with this low velocity abnoumal block as well as the deep faults.