关键词: 地震破裂, 活动断裂, 构造应力场, 甘肃

Abstract: The results of field investigations demonstrate that the 1927 Gulang M 8 earthquake caused six segments of ground ruptures which have different scales, strikes, mechanisms and grades. They composed a complex seismic fracture zone with plane shape distribtuion which is different from ruptures caused by strike slip faulting in western China. Among them four segements of rupture have the coincident locations with the epicentral and aftershock area and are distributed along the north rim of the Dongqingding mountain and the eastern section of the Huangcheng Shuangta fault and the north section of the Wuwei Tianzhu fault, forming the main rupture zone of the earthquake. The other two segments, as the secondary rupture zones are located in the middle section of the Huangcheng Shuangta fault and the Xishanpu Dishuiya fault, respectively. The four segments of the main rupture are the resluts from the uniform tectonic stress field and have consistent deformation mechanism. The Dongqingding extensional rupture zone was developed on the hanging wall of the Xiafangzhai Yanjiaxinzhuang reverse fault as a secondary fracture, while the main rupture was caused by the reverse faulting on the piedmont fluvial terrace.

Key words: Seismic rupture, Active fault, Tectonic stress field, Gangsu