摘要
通过分析首都圈数字地震台网的49个宽频带和甚宽带台站的远震SKS波形资料,采用最小切向能量的网格搜索法和叠加分析方法,求得每一个台站的SKS快波偏振方向和快、慢波的时间延迟,获得了首都圈地区上地幔各向异性图象.首都圈地区的各向异性快波方向基本上呈WNW-ESE方向,快、慢波时间延迟为0.56—1.56 s.研究表明,首都圈地区上地幔存在明显的各向异性,引起各向异性的主要原因是研究区受太平洋板块俯冲作用下软流圈物质变形,使得上地幔橄榄岩等晶体的晶格优势取向沿物质流动方向.另外,中国大陆受印度板块与欧亚板块的强烈碰撞,大陆西部地壳增厚隆起,同时造成物质东向挤出,使得首都圈地区上地幔物质沿快波方向变形.通过研究区各向异性快波方向和伸展运动方向与GPS测量得到的速度场对比分析,首都圈地区壳幔变形可能具有垂直连贯变形特征.
Based on the polarization analysis of teleseismic SKS waveform data recorded at 49 seismic stations involved in Capital Area Seismic Network, the SKS fast-wave polarization direction and the delay time between fast and slow wave arrival at each station were determined by use of a grid searching for the minimum transverse energy and a stacking analysis method, and then the image of upper mantle anisotropy in Capital area was acquired. In the study area, the fast-wave direction is basically in WNW-ESE direction, and the delay time falls into the range from 0.56 s to 1.56 s. The research result implies that the upper mantle anisotropy in Capital area is mainly caused by the subduction of the Pa- cific plate to Eurasian plate. The subduction of the Pacific plate has resulted in the asthenospheric deformation in Capital area, and made the alignment of upper mantle peridotite lattice parallel to the deformation direction. The collision between the plates made the crust of western China thickening and uplifting, and material eastwards extruding, then caused the upper mantle material flowing eastwards and made the direction of upper mantle deformation parallel to the fast-wave direction. The deformation model of the crust and upper mantle is possibly vertically coherent deformation by compare the fast-wave direction with the direction of lithospheric extension and GPS observed velocity.
出处
《地震学报》
CSCD
北大核心
2008年第6期551-559,共9页
Acta Seismologica Sinica
基金
The Special Project for the Fundamental Research and Development of Institute of Geophysics,China Earthquake Administration (DQJB06B06)
the National Natural Science Foundation of China (40334041)
the Special Program of the Ministry of Science and Technology of China (2006FY110100)
Contribution No.08FE3011,Institute of Geophysics,China Earthquake Administration.
关键词
首都圈地区
SKS波
各向异性
快波方向
变形
Capital area
SKS wave splitting
anisotropy
fast-wave direction
deformation
