首都圈地区SKS波分裂研究
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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 fails 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 subduetion of the Pacific plate has resulted in the asthenospheric deformation in Capital area,and made the alignment of up- per 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 flow- ing 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.
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 fails 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 subduetion of the Pacific plate has resulted in the asthenospheric deformation in Capital area,and made the alignment of up- per 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 flow- ing 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.
引文
常利军，王椿镛，丁志峰，周民都，杨建思，徐智强，姜旭东，郑秀芬．2008．青藏高原东北缘上地幔各向异性研究[J]．地球物理学报，51(2)：431-438．
常利军，王椿镛，丁志峰．2006．云南地区SKS波分裂研究[J]．地球物理学报，49(1)：197-204．
邓晋福，赵海玲，莫(?)学，吴宗絮，罗照华．1996．中国大陆根—柱—大陆动力学的钥匙[M]．北京：地质出版社：59-82．
丁志峰，曾融生．1996．青藏高原横波分裂的观测研究[J]．地球物理学报，39(2)：211-219．
高原，郑斯华，周蕙兰．1999．唐山地区快剪切波偏振图像及其变化[J]．地球物理学报，42(2)：228-232．
姜枚，许志琴，Hirm A，刘妍，董英君，薛光琦，钱辉．2001．青藏高原及其部分邻区地震各向异性和上地幔特征[J]．地球学报．22(2)：111-116．
赖院根，刘启元，陈九辉，刘洁，李顺成，郭飙，黄志斌．2006．首都圈地区横波分裂与地壳应力场特征[J]．地球物理学报，49(1)：189-196．
吕庆田，马开义·姜枚．1996．青藏高原南部下的横波各向异性[J]．地震学报，18(2)：215-223．
罗艳，黄忠贤，彭艳菊，郑月军．2004．中国大陆及邻区SKS波分裂研究[J]．地球物理学报，47(5)，812-821．
马宗晋，陈鑫连，叶叔华，赖锡安，魏子卿，陈俊勇，宁津生，许厚泽，丁国瑜．2001．中国大陆现今地壳运动的GPS研究[J]．科学通报．46(13)：1118-1120．
牛之俊，王敏，孙汉荣，孙建中，游新兆，甘卫军．薛贵江，郝晋新．辛少华，王永清，王永祥．李柏．2005．中国大陆现今地壳运动速度场的最新观测结果[J]．科学通报，50(8)：839-848．
彭艳菊，黄忠贤，苏伟，郑月军．2007．中国大陆及邻区海域地壳上地幔各向异性研究[J]．地球物理学报．50(3)：752-759．
齐诚，赵大鹏，陈颐，陈棋福，王宝善．2006．首都圈地区地壳P波和S波三维速度结构及其与大地震的关系[J]．地球物理学报，49(3)；805-815．
邱瑞照，邓晋福，周肃．李金发，肖庆辉，吴宗絮，刘翠．2004．华北地区岩石(?)类型：地质与地球物理证据[J]．中国科学(D辑)，34(8)：689-711．
王椿镛，常利军，吕智勇，秦嘉政，苏伟，Silver P G，Flesch M L．2007．青藏高原东部上地幔各向异性及相关的壳幔耦合型式[J]．中国科学(D辑)，37(4)：495-503．
王涛，郑亚东，张进江，王新社，曾令森，童英．2007．华北克拉通中生代伸展构造研究的几个问题及其在岩石(?)减薄研究中的意义[J]．地质通报，26(9)：1154-1166．
吴晶，高原，陈运泰，黄金莉．2007．首都(?)西北部地区地壳介质地震各向异性特征初步研究[J]．地球物理学报．50(1)：209-220．
郑斯华，高原．1994．中国大陆岩石层的方位各向异性[J]．地震学报，16(2)：131-140．
朱日样．2007．地球内部结构探测研究：以华北克拉通为例[J]．地球物理学进展，22(4)：1090-1100．
An M,Shi Y.2006.Lithospheric thickness of the Chinese continent[J].Phys Earth Planet Ints,159:257-266.
Gripp A E,Gordon R G.2002.Young tracks of hotspots and current plate velocities[J].Geophys J Int,150:321-361.
Huang J,Zhao D.2004.Crustal heterogeneity and seismotectonics of the region around Beijing[J].Tectonophysics, 385;159-180.
Liu K H,Gao S S,Gao Y,Wu J.2008.Shear wave splitting and mantle flow associated with the deflected Pacific slab beneath northeast Asia[J].J Geophys Res,113,B01305,doi:10.1029/2007JB005178.
McNamara D,Owens T,Silver P G,Wu F T.1994.Shear-wave anisotropy beneath the Tibetan Plateau[J].J Geophys Res,99:13655-13665.
Silver P G,Chan W W.1991.Share-wave splitting and subcontinental mantle deformation[J].J Geophys Res,96: 16429-16454.
Vinnik L P,Farra V,Romanowicz B.1989.Azimuthal anisotropy in the Earth from observations of SKS at Geoscope and NARS broadband stations[J].Bull Sesim Soc Amer,79:1542-1558.
Vinnik L P,Makeyeva L I,Miler A,Usenko A Y.1992.Global patterns of azimuthal anisotropy and deformations in the continental mantle[J].Geophys J Int,111:433-447.
Wolfe C J,Silver P G.1998.Seismic anisotropy of oceanic upper mantle:Shear wave splitting methodologies and obser- vations[J].J Geophys Res,103(B1):749-771.
Zhao L,Zheng T Y.2005.Using shearwave splitting measurements to investigate the upper mantle anisotropy beneath the North China Craton:Distinct variation from east to west[J].Geophys Res Lett,32,L10309,doi:10.1029/ 2005GL022585.
常利军，王椿镛，丁志峰．2006．云南地区SKS波分裂研究[J]．地球物理学报，49(1)：197-204．
邓晋福，赵海玲，莫(?)学，吴宗絮，罗照华．1996．中国大陆根—柱—大陆动力学的钥匙[M]．北京：地质出版社：59-82．
丁志峰，曾融生．1996．青藏高原横波分裂的观测研究[J]．地球物理学报，39(2)：211-219．
高原，郑斯华，周蕙兰．1999．唐山地区快剪切波偏振图像及其变化[J]．地球物理学报，42(2)：228-232．
姜枚，许志琴，Hirm A，刘妍，董英君，薛光琦，钱辉．2001．青藏高原及其部分邻区地震各向异性和上地幔特征[J]．地球学报．22(2)：111-116．
赖院根，刘启元，陈九辉，刘洁，李顺成，郭飙，黄志斌．2006．首都圈地区横波分裂与地壳应力场特征[J]．地球物理学报，49(1)：189-196．
吕庆田，马开义·姜枚．1996．青藏高原南部下的横波各向异性[J]．地震学报，18(2)：215-223．
罗艳，黄忠贤，彭艳菊，郑月军．2004．中国大陆及邻区SKS波分裂研究[J]．地球物理学报，47(5)，812-821．
马宗晋，陈鑫连，叶叔华，赖锡安，魏子卿，陈俊勇，宁津生，许厚泽，丁国瑜．2001．中国大陆现今地壳运动的GPS研究[J]．科学通报．46(13)：1118-1120．
牛之俊，王敏，孙汉荣，孙建中，游新兆，甘卫军．薛贵江，郝晋新．辛少华，王永清，王永祥．李柏．2005．中国大陆现今地壳运动速度场的最新观测结果[J]．科学通报，50(8)：839-848．
彭艳菊，黄忠贤，苏伟，郑月军．2007．中国大陆及邻区海域地壳上地幔各向异性研究[J]．地球物理学报．50(3)：752-759．
齐诚，赵大鹏，陈颐，陈棋福，王宝善．2006．首都圈地区地壳P波和S波三维速度结构及其与大地震的关系[J]．地球物理学报，49(3)；805-815．
邱瑞照，邓晋福，周肃．李金发，肖庆辉，吴宗絮，刘翠．2004．华北地区岩石(?)类型：地质与地球物理证据[J]．中国科学(D辑)，34(8)：689-711．
王椿镛，常利军，吕智勇，秦嘉政，苏伟，Silver P G，Flesch M L．2007．青藏高原东部上地幔各向异性及相关的壳幔耦合型式[J]．中国科学(D辑)，37(4)：495-503．
王涛，郑亚东，张进江，王新社，曾令森，童英．2007．华北克拉通中生代伸展构造研究的几个问题及其在岩石(?)减薄研究中的意义[J]．地质通报，26(9)：1154-1166．
吴晶，高原，陈运泰，黄金莉．2007．首都(?)西北部地区地壳介质地震各向异性特征初步研究[J]．地球物理学报．50(1)：209-220．
郑斯华，高原．1994．中国大陆岩石层的方位各向异性[J]．地震学报，16(2)：131-140．
朱日样．2007．地球内部结构探测研究：以华北克拉通为例[J]．地球物理学进展，22(4)：1090-1100．
An M,Shi Y.2006.Lithospheric thickness of the Chinese continent[J].Phys Earth Planet Ints,159:257-266.
Gripp A E,Gordon R G.2002.Young tracks of hotspots and current plate velocities[J].Geophys J Int,150:321-361.
Huang J,Zhao D.2004.Crustal heterogeneity and seismotectonics of the region around Beijing[J].Tectonophysics, 385;159-180.
Liu K H,Gao S S,Gao Y,Wu J.2008.Shear wave splitting and mantle flow associated with the deflected Pacific slab beneath northeast Asia[J].J Geophys Res,113,B01305,doi:10.1029/2007JB005178.
McNamara D,Owens T,Silver P G,Wu F T.1994.Shear-wave anisotropy beneath the Tibetan Plateau[J].J Geophys Res,99:13655-13665.
Silver P G,Chan W W.1991.Share-wave splitting and subcontinental mantle deformation[J].J Geophys Res,96: 16429-16454.
Vinnik L P,Farra V,Romanowicz B.1989.Azimuthal anisotropy in the Earth from observations of SKS at Geoscope and NARS broadband stations[J].Bull Sesim Soc Amer,79:1542-1558.
Vinnik L P,Makeyeva L I,Miler A,Usenko A Y.1992.Global patterns of azimuthal anisotropy and deformations in the continental mantle[J].Geophys J Int,111:433-447.
Wolfe C J,Silver P G.1998.Seismic anisotropy of oceanic upper mantle:Shear wave splitting methodologies and obser- vations[J].J Geophys Res,103(B1):749-771.
Zhao L,Zheng T Y.2005.Using shearwave splitting measurements to investigate the upper mantle anisotropy beneath the North China Craton:Distinct variation from east to west[J].Geophys Res Lett,32,L10309,doi:10.1029/ 2005GL022585.
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