南北地震带中段深部构造与地震

THE DEEP STRUCTURE AND EARTHQUAKE OF THE CENTRAL SEGMENT IN THE NORTH-SOUTH SEISMIC BELT

南北地震带中段位于中国大陆腹部，是青藏块体、华北块体和扬子块体的中间枢纽部位。根据该区布格重力异常图，采用Ｐａｒｋｅｒ’ｓ三维位场方法进行莫氏面反演并计算该区不同窗口的剩余场，推断和解释了４条岩石圈断裂，进而研究它们与地震的关系。深部孕震的有利部位是：区域性重力梯级带；地壳厚度变异带或莫氏回等值线发生转折的部位或莫氏面隆起的边缘；重力正负剩余异常的零值线附近以及活动的深大断裂。

The region is located in the belly of Chinese mainland,which is a pivot zone of the Qinghai-Tibet block, the North China block ahd the Yangtze block. We inverses the crustal thickness of the central segment in the North-South belt by Bouguer gravity anomaly map,using the Parker's three demension potential field method. We calculated the residual gravity anomaly with different windows. The four lithospheric fractures in the research region were inferred and interpreted.The paper has studied the relationship between the deep structure and the earthquakes.The favourable conditions of the deep development of the earthquakes are:the gravity anomaly gradient belt;the crustal thick variable belt;the suddenly turning position and the elevated margin of the Mohe surface;the zero line vicinity of the residual anomaly and the deep and large activity fractures..