汶川地震破裂带地壳速度结构研究  

Study on the crustal structures beneath Wenchuan earthquake rupture zone

作　　者：沈旭章[1,2] 梅秀苹[1] 杨辉[3] 

机构地区：[1]中国地震局兰州地震研究所,兰州730000 [2]中国地震局地震预测研究所兰州科技创新基地,兰州730000 [3]中国地震局台网中心,北京100866

出　　处：《地球物理学进展》2011年第2期477-488,共12页Progress in Geophysics

基　　金：中国地震局地震预测研究所基本科研业务费(2009A19);国家自然科学基金项目(40904014)资助

摘　　要：利用分布在汶川地震破裂带上三个固定台站两年的远震接收函数,结合该区域已有面波频散结果,首先确定了各台站下方不同方位地壳的厚度、波速比和纵波平均速度,进而构建初始模型,对各台站下方不同方位地壳速度结构进行了线性反演.结果表明:位于汶川地震破裂带两端单台下方地壳结构的横向非均匀性较强,各方位接收函数差异较大,而破裂带中部台站的地壳速度结构横向较为均匀;在汶川地震破裂起始点附近的台站下方,反演结果显示出中下地壳中明显的低速区,该结果和已有层析成像结果相一致,而在破裂带中部和终点的地壳中没有发现明显低速层.据此推断:青藏东部低速的流动性物质已经延伸到了龙门山地区,汶川地震的起始破裂点可能就是这种低速流动物质延伸的终点.The teleseismic receiver functions from 3 permanent stations on the Wenchuan earthquake rupture zone are combined with surface wave dispersions to estimate the crustal thickness, Vp to Vs ratio and average Vp beneath each station. Then, the initial model of the crust is constructed and the crustal structures of different azimuth beneath the station are inverted. The results indicate the obvious heterogeneity beneath the two stations in the start and the end of the rupture, the observed receiver functions of these 2 stations are different in different azimuth, and the structure beneath the station in the middle of the rupture is homogeneous. The inverted results show that the low velocity zone in the middle-lower crust is found beneath the station which is nearest to the main shock; this result is coincident with the result of tomography. No other low velocity zone is found beneath other two stations. We estimate that the fluids with low velocity beneath eastern Tibet may reach to the Longmenshan region, and the initial rupture point of the Wenchuan earthquake may be the termination of the low velocity fluids.

关 键 词：汶川地震破裂带 接收函数 面波 地壳低速层 

分 类 号：P315[天文地球—地震学]