2013年甘肃岷县漳县6.6级地震震害分布特征及发震构造分析

DISTRIBUTION OF THE RELATED DISASTER AND THE CAUSATIVE TECTONIC OF THE MINXIAN-ZHANXIAN M_S6.6 EARTHQUAKE ON JULY 22,2013,GANSU,CHINA

2013年7月22日,甘肃岷县漳县M S6.6地震发生在南北地震带的中北段,东昆仑断裂和西秦岭北缘断裂是该地区复杂多样的构造几何特征中2条主要的边界控制断裂。这次地震的震害分布与临潭-宕昌断裂的走向基本一致,为长轴走向NWW的椭圆,极震区内严重破坏范围也完全位于该断裂带内,这与临潭-宕昌断裂复杂的几何结构密切相关,也说明地震的发生是多条次级断裂共同作用的结果。综合分析认为,受西秦岭北缘断裂带向南侧的扩展和青藏高原向NE扩展过程中东昆仑断裂带的NE向挤压作用共同影响下的临潭-宕昌断裂是这次地震的发震构造。

On July 22,2013, the Minxian-Zhanxian Ms 6.6 earthquake occurred at the central-northern part of the South-North Seismic Belt. In the area, complicated structural geometries are controlled by major strike-slip fault zones,i, e. the Eastern Kunlun Fault and the Northern Frontal Fault of West Qinling. The distribution of related seismic disasters, namely, the ellipse with its major axis trending NWW, is in good accord with the strike of the Lintan-Tanchang Fault. Severe damages in the meizoseismal area of the Minxian-Zhangxian Ms 6.6 earthquake are located within the fault zone. So it is considered that the earthquake related damages are closely related to the complicated geometry of the Lintan-Tanchang Fault,and it also indicates that the earthquake is the outcome of joint action of its secondary faults. Based on field investigations, and by integrating the results of previous studies on active tectonics, structural deformation and geophysical data, it can be inferred that the southward extension of the Northern Frontal Fault of West Qinling and the northeastward extrusion of the Eastern Kunlun Fault in the process of northeastward growth of Tibetan plateau are the main source of tectonic stress. Basic tectonic model is provided for strong earthquake generation on the Lintan-Tanchang Fault.