中国大陆中东部地区基于背景噪声的瑞利波层析成像  

Rayleigh wave tomography from ambient noise in Central and Eastern Chinese mainland

作　　者：郑现[1] 赵翠萍[1] 周连庆[1] 郑斯华[1] 

机构地区：[1]中国地震局地震预测研究所,北京100036

出　　处：《地球物理学报》2012年第6期1919-1928,共10页Chinese Journal of Geophysics

基　　金：国家科技支撑项目(2008BAC38B02);地震预测研究所基本科研业务费专项(2011TES0101)资助

摘　　要：本研究使用了中国大陆中东部地区494个分布基本均匀的宽频带地震台站和7个中国大陆周边地区IRIS台站资料,反演得到了中东部地区高分辨率的瑞利面波层析成像结果.本文使用这些台站记录到的从2009年1月到2010年9月的垂直分量连续波形数据,首先通过对台站对间进行波形互相关和叠加运算,计算得到各台站对间的经验格林函数.然后用时频分析法提取了约125000条台站对间的频散曲线,并剔除了经验格林函数信噪比小于10的频散曲线.最后反演得到了研究区周期8～40s、分辨率达0.5°的瑞利波群速度分布图像.不同周期的速度分布图像显示,研究区瑞利波群速度分布与地质构造特征具有较好的相关性.8～20s的瑞利波群速度在研究区内主要盆地表现为低速分布,而在造山带呈现高速分布;25～40s的瑞利波群速度图中,存在一条北北东—南南西向的分界线,该分界线与中国大陆东部的地壳厚度突变带基本吻合.25s以下周期,华北平原的显著低速区形态与该地区早第三纪以来的断块分布构造一致.揭示了盆地下方介质结构强烈的非均匀性,也与较厚的沉积层分布有关.低速的四川盆地中部,显示出显著的高速特征,揭示了四川盆地下方基底的上隆特征;20s以下周期的群速度图像中,鄂尔多斯盆地西北部速度低于东南部,揭示出其地壳中上部介质结构的横向不均匀性.We present high resolution ambient noise tomography of central and eastern China using vertical component seismograms recorded by 494 evenly distributed broadband stations from China National Seismic Network and regional networks and 7 IRIS stations. 21 months of continuous data are used from January 2009 to September 2010. We first obtain empirical Green functions （EGFs） after cross-correlation and stacking between all possible station-pairs. Then we retrieve about 125000 Rayleigh wave dispersion curves using a frequency-time analysis method and reject those with SNR〈10. Finally, we invert for Rayleigh wave group velocity maps from 8s to 40 s. The resolution can reach to about 0. 5° at these periods. Our group velocity maps agree well with known geological and tectonic features. Major basins in the study area are delineated by low velocities at short periods （8420 s）, while orogenic belt and uplift areas are manifested by high velocities. An NNE-SSW trending boundary between high and low velocities can be clearly seen at longer periods （25-40 s）, which coincides with the well-known Gravity Lineation. North China plain shows remarkable low velocity at group velocity maps below 25s. The shape of low velocity zone coincides with the block distribution of the plain since Paleogene. A relative high velocity zone is observed in the central part of low velocity Sichuan basin, reveals an uplifted basement beneath the basin. The velocity in the northwest of Ordos basin is lower than that in southeast in the tomography maps under 20 s, revealing the lateral heterogeneity in mid-upper crust.

关 键 词：中国大陆中东部 背景噪声 面波层析成像 地壳上地幔 

分 类 号：P315[天文地球—地震学]