阿拉善地块南部雅布赖山前断裂的运动学特征及意义初探  

NEOTECTONICS AND KINEMETICS ALONG THE YABRAI RANGE-FRONT FAULT IN THE SOUTH ALASHAN BLOCK AND ITS IMPLICATIONS FOR REGIONAL TECTONICS

作　　者：俞晶星[1] 郑文俊[1] 雷启云[1,2] 邵延秀[1,3] 葛伟鹏[1,3] 马严[1] 李又娟[1] 

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]宁夏回族自治区地震局,银川750001 [3]中国地震局兰州地震研究所,兰州73000

出　　处：《地震地质》2013年第4期731-744,共14页Seismology and Geology

基　　金：中国地震局地质研究所基本科研业务专项(IGCEA1220);中国地震局地震行业科研专项(201008003);国家自然科学基金(41372220)共同资助

摘　　要：雅布赖山前断裂位于阿拉善块体中部的雅布赖山东南侧,断裂全长约120km,整体走向为N60°E,倾向SE,正断性质,局部发现左旋走滑特征.通过卫星影像解译及野外地质填图,并结合断裂几何结构与断错地貌特征将断裂分为3段：雅布赖盐厂段（西南段）、阿贵庙段（中段）、海布勒格段（东北段）.其中,雅布赖盐厂段长约35km,新活动特征明显,最新一次事件陡坎高度约1m,保存了新鲜的自由面,表明最后一次事件离逝时间较短.阿贵庙段长约31km,断裂整体沿基岩山前分布,几何结构单一,部分地段距山前1 ～2km处发现分支断裂.海布勒格段长约15km,断错多级地貌面,局部发现最新地表破裂,但不连续,其陡坎高0.5～1.5m.雅布赖山前断裂以正断性质为主,它的形成主要是受到NW-SE方向的区域拉张作用,局部的左旋特征可能是由于受到青藏高原往NE向扩展的影响.The Yabrai range-front fault is a normal fault,which is about 120km long,trends N60°E and distributes along the southeast margin of the Alashan block.In this paper,we focus on the geomorphology and kinematics of the Yabrai range-front fault,and discuss the implications of the fault for the regional tectonics.This fault consists of three segments and the most active one is located in the southwest,which has a length of about 35km.The about 1 ～ 2m-high scarp,stretching almost the full segment,might be the result of the latest earthquake event.Fresh free surface indicates that the elapsed time of the last event should not be long.The middle segment is about 31km in length.The results suggest that just a single fault is developed along the piedmont of the Yabrai Shan,and there is no evidence of recent activity on this fault.In contrast to the simple geometric structure of the middle segment,the northeast segment consists of several faults.The scarps of the most recent earthquake event,which are clear but discontinuous,are about 0.5 ～ 1.5m high and some are up to 2m.Although the scarps along the southwest and northeast segments of the fault are similar,it is difficult to suggest they are caused by the same earthquake without precise dating.The seismic reflection profile suggests that the Yabrai range-front fault came into being as a normal fault in Cretaceous,when the Tibetan plateau did not emerge at that time.Therefore,we conclude that the Yabrai range-front fault is not the consequence of the Indo-Asian collision.But this region plays a great role in constraining the tectonic evolution of the Alashan block and therefore,the Tibetan plateau.

关 键 词：断裂分段 断错地貌 运动学特征 雅布赖山前断裂 阿拉善块体南缘 

分 类 号：P312.5[天文地球—固体地球物理学]