基于Love波相速度反演南北地震带地壳上地幔结构  

The crustal and upper mantle structure beneath the South-North seismic zone from the inversion of Love wave phase velocity

作　　者：徐小明[1] 丁志峰[1,2] 叶庆东[3] 吕苗苗[1] 

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局地球物理研究所地震观测与地球物理成像重点实验室,北京100081 [3]中国地震局第一监测中心,天津300180

出　　处：《地球物理学报》2015年第11期3928-3940,共13页Chinese Journal of Geophysics

基　　金：地震行业科研专项(201008001和201308011)资助

摘　　要：收集了南北地震带区域地震台网中292个地震台站2008年1月至2011年3月期间的地震波形数据,由频时分析方法提取了Love波相速度频散曲线,经过反演得到了研究区内的Love波相速度分布.根据Love波纯路径频散,采用线性反演方法对0.25°×0.25°的网格点进行了一维S波速度结构反演,利用线性插值获取了南北地震带地区的三维S波速度结构.结果显示了松潘—甘孜地体和川滇菱形块体地区的下地壳具有明显的S波低速层分布,该异常分布特征支持解释青藏高原隆升及其地壳物质运移的下地壳流模型.在100至120km深度上,川滇菱形块体西北部呈现较强的S波高速异常,这可能是印度岩石圈板块沿喜马拉雅东构造结下插至该区域所致,该区域下地壳的低速软弱物质与上地幔的高速强硬物质形成了鲜明对比,暗示了地壳和上地幔可能具有不同的构造运动和变形方式,这为该区域的壳幔动力学解耦提供了条件.The South-North Seismic Zone（SNSZ）located the eastern margin of Tibetan plateau is an active tectonic zone between the west of the rising plateau and the east of the stable blocks,where the regional tectonic is quite complex and the seismicity is very high.The crustal and mantle structure beneath the SNSZ has the scientific significance for indicating the uplift mechanism of the Tibetan plateau and the interaction between the Tibetan plateau and its adjacent blocks.The tomographic method was used to estimate the crustal and mantle structure beneath the SNSZ.A two-step inversion scheme was adopted to obtain the S-wave velocity structure.Firstly,we constructed phase velocity distributions by inverting pure path dispersions of Love wave at different periods.Secondly,we determined the S-wave velocity structure at different depths from the acquired phase velocities.We collected the seismic waveform data recorded between January 2008 and March 2011by292 stations from the Chinese Provincial Digital Seismic Networks,measured the Love wave phase velocity dispersion curves with Frequency-Time Analysis and constructed the distributions of the Love wave phase velocity beneath the SNSZ.From the pure path dispersions of Love wave phase velocity,the one-dimension S-wave velocity was inverted by the linearized inversion program at each node on a 0.25°×0.25°grid.Then these one-dimension S-wave velocity were assembled together to obtain the three-dimension S-wave velocity structure.Our results suggested that the significantly low velocity layer of S-wave existed in SongpanGarzêterrane and Chuandian diamond block.The characteristic of the low velocity anomaly supported the lower crust flow model for explaining the uplift of the Tibetan plateau and its crustal materials movement.The high S-wave velocity anomaly was presented in northwestern Chuandian diamond block at the depth 100 to 120km,which maybe attribute to the underthrust plate of the India lithosphere along the Himalayas east structural knot.The obvious comparison b

关 键 词：南北地震带 层析成像 LOVE波 互相关函数 相速度 

分 类 号：P315[天文地球—地震学]