山西大宁县典型滑坡体地貌特征与降雨和强震关系

Geomorphic Characteristics of Typical Landslides in Daning County, Shanxi Province, China, and Its Relationship with Rainfall and Strong Earthquakes

摘要:

山西大宁县位于山西省吕梁山南端，境内沟壑纵横，具有独特的黄土高原地形地貌特征。在该地区进行地质灾害调查，以查明灾害分布、形成原因和隐患情况。应用地貌学的有关原理，结合遥感影像解译，在义亭河的支流河谷两岸0.3 km²（575 m×526 m）范围内发现并确认了2个大型和2个中型滑坡体。滑坡体均为基岩与上方的黄土沉积层整体滑下，滑坡体沿河流流动的方向发生一定程度的扭转，滑面近于直立，滑动方向与河流流向一致，没有形成堰塞湖。对滑坡体与周围地貌特征，以及河道被改动的方向特征研究认为：①4个滑坡体是在不同的地质时期形成；②其中1个滑坡体明显受到一条断裂的影响；③其它3个滑坡体，可能是在河流侵蚀搬运作用加强，导致的"重力塌陷"，及河流流向作用牵引的动力学作用下，经过较漫长的时间形成；④在距离该地区约60 km的洪洞地震、临汾地震，以及距离该地区230余公里的华县地震，这三次8级地震过程中，地震应力可能加剧了滑坡体的发生或滑动；⑤未来该滑坡体，仍然可能在非常规的外界条件下，如强降雨或地震应力等的影响下，出现加速滑动的可能。

Abstract:

Daning County is located at the southern end of Lüliang Mountain, Shanxi Province, with unique topographic and geomorphic characteristics of the loess plateau. The investigation of geological hazards was conducted in the area to determine the distribution, causes, and hidden dangers of disasters. Through the application of the relevant principles of geomorphology and remote sensing image interpretation, two large-sized and two medium-sized landslide bodies were detected and confirmed in the 0.3 km² (575 m×526 m) range of the two banks of the Yiting River. The characteristics of the four landslide bodies and their surrounding landform, as well as the change in the direction of the river course, are analyzed. We propose the following:(1) The four landslide bodies were formed in different geological periods. (2) One landslide body was obviously affected by a fault. (3) The three other landslide bodies were formed over a long period of time under the dynamic action of "gravitational collapse" and river flow direction. (4) The stress of three M_S8.0 earthquakes, i.e., the Hongdong and Linfen earthquakes (60 km from the area) and the Huaxian earthquake (more than 230 km from the area), aggravated the occurrence of the landslides. (5) Future studies should consider the possibility that landslides are accelerated by unconventional external conditions, such as heavy rainfall or earthquake stress.