南北构造带天水、武都强震区地壳和上地幔顶部结构  

Structure of Crust and Upper Mantle in Tianshui-Wudu Strong Earthquake Region of North-South Tectonic Belt

作　　者：赖晓玲[1] 李松林[1] 宋占龙[1] 樊计昌[1] 刘明军[1] 何加勇[2] 

机构地区：[1]中国地震局地球物理勘探中心,河南郑州450002 [2]中国地震局地球物理研究所,北京100081

出　　处：《地球科学（中国地质大学学报）》2009年第4期651-657,共7页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos.40774043,40674043,90814001);财政部“南北地震带紧急强化震情跟踪”专项经费;中国地震局地球物理勘探中心论著RCEG0806资助

摘　　要：利用两条相互垂直的高分辨地震折射/宽角反射剖面和相应的非纵观测的多个扇形剖面取得的人工地震资料,研究天水和武都8级大震区的地壳和上地幔顶部结构和构造.二维剖面结果显示,地壳沿垂向可分为上地壳和下地壳两大层.上地壳中部存在低速层,层内介质速度比背景值低0.3～0.5km/s.莫霍面深度大约为46～48km.NE向的天水-武都剖面下地壳速度在横向上变化剧烈,NW向的成县-武山剖面,在礼县以西,Moho面和C界面有被上涌物质改造过的迹象.三维速度成像显示,在105°E附近,从7至11km的深度范围内,存在一条近NS向的断裂带,在该带的两侧速度结构有明显的差异,西侧为低速异常,而东侧为高速异常,这一近NS向的断裂带与二维剖面的下地壳深断裂在位置上很接近.该地区的几个8级大震均发生在105°E附近,并且呈一近NS条带.The structure of crust and upper mantle in Tianshui-Wudu strong earthquake region is studied by using DSS data from two cross high resolution refraction / wide angle reflection profiles and corresponding fan profiles. The 2-D result shows that the crust can be vertically divided into two layers： upper crust and lower crust. There exists a low velocity layer in the upper crust with velocity difference of 0. 3-0. 5 km/s. The depth of Moho is about 46-48 km There is a strong lateral variation in the lower crust along the NE Tianshui-Wudu profile. And along the NW Chengxian-Wushan profile, there are some evidences showing that the Moho and C discontinuities are changed by substances from the deep layer. The 3-D result shows that there is a fault with near NS strike at the depth of 7-11 km near 105°E. The velocities at the two sides of this fault are quite different： low velocity at the west side and high velocity at the east side. This NS fault is very close to the deep fault of 2-D profile. All the large earthquakes occurred near 105°E and formed a NS belt.

关 键 词：南北构造带 地震测深 强震区 地震勘探 

分 类 号：P631.4[天文地球—地质矿产勘探]