海原、六盘山断裂带至银川断陷第四纪构造应力场分析

QUATERNARY TECTONIC STRESS FIELD IN THE REGION OF HAIYUAN LIUPANSHAN FAULT ZONE TO YINCHUAN FAULT DEPRESSION

利用断层滑动资料反演构造应力张量从而确定出海原、六盘山断裂带至银川断陷的第四纪两期构造应力场 :早更新世末期以前 ,为北东—南西挤压型构造应力场 ,由此造成该地区断裂活动主要以逆断为主 ;早更新世末期至中更新世以后 ,构造应力场发生了调整 ,主压应力方向由早期的北东—南西改变为北东东—南西西 ,应力结构由挤压型转变为走滑型 ,并导致断裂活动由早期的逆断为主变为走滑为主 ,这种应力场格局一直持续至今。研究区现代构造应力场可划分为 :海原断裂带走滑应力区、六盘山逆断

By inversion of fault slip data, it is suggested that stress field of the region from the Haiyuan Liupanshan fault zone to the Yingchuan fault depression has two major stages. Before early Pleistocene the maximum principal compression stress direction was NE SW, the stress regime was reverse type, witch resulted in dominating reverse faults. After early to middle Pleistocene the tectonic stress field had a readjustment, the maximum principal compression stress direction was changed from NE SW to NEE SWW, the stress regime from reverse type to strike slip type too, and the former reverse faults became strike slip faulting, which continues much the same today. The recent tectonic stress field of the studied area can be divided into strike slip region of Haiyuan fault zone, mixed region of reverse and strike slip of Liupanshan and extension region of Yinchuan fault depression.