利用瑞雷面波反演华北克拉通东北部边界的岩石圈结构  

Lithospheric structure beneath northeastern boundary region of the North China Craton from Rayleigh wave dispersion inversion

作　　者：李明明[1,2] 何玉梅[1] 

机构地区：[1]中国科学院地质与地球物理研究所,中国北京100029 [2]中国科学院研究生院地球科学学院,中国北京100049

出　　处：《地震学报》2011年第2期143-155,270,共13页Acta Seismologica Sinica

基　　金：国家自然科学基金项目(40774041);国家自然科学基金重大研究计划(90814002)共同资助

摘　　要：运用瑞雷面波相速度频散曲线分析和反演得到了华北克拉通东北部边界及其邻近区域岩石圈的精细S波速度结构.利用11个地震事件、60个台站的瑞雷面波波形资料,得到了周期从25—150s的相速度频散曲线,并且通过线性反演方法得到了深度从40—300km的S波速度结构.结果表明,该研究区域S波速度存在强烈的不均匀性.从东南部的燕山—辽东半岛区域到西北部的兴蒙造山带,岩石圈厚度有显著的变化,且在索伦缝合带附近变化最快.同时索伦缝合带下方的岩石圈和软流圈S波速度差异比其它地区要小.基于S波速度结构,我们推测:①太平洋俯冲在华北克拉通东北部边界岩石圈的破坏过程中起着重要的作用,但是它对索伦缝合带西北部的区域影响较小;②索伦缝合带附近岩石圈厚度的快速变化造成了局部的地幔物质上涌,从而造成了减压熔融,降低了岩石圈的S波速度.We have inverted Rayleigh wave dispersion data to produce a high resolution image of the S-wave velocity structure of the lithosphere beneath northeast boundary region of the North China Craton and adjacent areas.Based on waveform data recorded from 60 stations and 11 events,Rayleigh wave phase velocities were measured at periods from 25 to 150 s.The phase velocities were utilized in subsequent inversion to solve for the S-wave velocity structure from 40 km down to 300 km depth.The result shows strong lateral seismic heterogeneity.The lithospheric thickness increases sharply across the Solonker suture from the Yanshan--Liaoning region to the Xing＇an--Mongolian orogen.In addition,the S-wave velocity contrast between the lithosphere and asthenosphere beneath the Solonker suture is smoothed,compared to other areas.Based on our S-wave velocity image,we speculate that ① Pacific plate subduction may play an important role in lithospheric thinning in northeastern boundary region of the North China Craton,while the far field effect of this subduction is not evident to the northwest of Solonker suture;② the lithospheric thickness change beneath the Solonker suture may induce regional upwelling mantle flow and decompression melting,decreasing the S-wave velocity of the lithosphere.

关 键 词：瑞雷面波 华北克拉通 索伦缝合带 岩石圈 

分 类 号：P315.31[天文地球—地震学]