鄂尔多斯块体及周缘上地幔各向异性研究
摘要
对布设在鄂尔多斯块体及周缘的固定和流动宽频带地震台网共111个台站记录作远震SKS(SKKS)波形资料偏振分析,采用最小切向能量的网格搜索和叠加分析求得每一个台站的SKS(SKKS)快波偏振方向和快、慢波的延迟时间,获得了鄂尔多斯块体及周缘上地幔各向异性图像.在鄂尔多斯块体西缘和北缘,各向异性的快波方向为NW-SE方向,一致性较好;在鄂尔多斯多斯块体南缘,快波方向主要是NWW-SEE和近EW方向;在鄂尔多斯块体东缘,快波方向总体表现为近EW方向,间有NEE-SWW方向和NWW-SEE方向.在鄂尔多斯块体内部,快波方向在北部是近NS方向,而南部则是近EW方向.快、慢波的时间延迟范围是0.48～1.50s,鄂尔多斯块体内部的时间延迟平均值小于其周缘地区.通过分析研究区各向异性特征,认为构造稳定的鄂尔多斯块体内部的各向异性主要来自于古老的华北克拉通保存的"化石"各向异性;青藏高原东北缘向NE方向的推挤,造成岩石圈NW-SE方向的拉张伸展,鄂尔多斯块体西缘和北缘下的上地幔物质沿NW-SE方向发生了形变,使得上地幔中橄榄岩的晶格排列方向平行于物质形变的方向;在鄂尔多斯块体南缘,刚性的华北块体和扬子块体碰撞作用,使得各向异性快波方向平行于两个刚性块体的碰撞边界和秦岭造山带的走向.结合该区域绝对板块运动和速度结构研究,认为在秦岭造山带下可能存在一个青藏高原物质东流的地幔流通道;在鄂尔多斯块体东缘的汾河地堑和太行山,相对复杂的各向异性特征可能由于西太平板块俯冲、区域伸展构造、造山运动等共同作用引起的.对于YCI台得到的各向异性参数(快波方向变化范围是45°～106°,时间延迟变化范围是0.6～1.5s)随事件反方位角呈现出π/2周期的变化,符合双层各向异性模型.基于0.125Hz的主频和实测的各向异性参数,我们模拟得到了最佳的双层各向异性模型,下层φlower=132°,δtlower=0.8s,上层φupper=83°,δtupper=0.5s.上层各向异性归功于古老克拉通保留的"化石"各向异性,下层各向异性则受到了青藏高原东北缘NE方向推挤导致的岩石圈NW-SE方向的拉张伸展作用.通过该区域各向异性快波方向与全球定位系统(GPS)的观测结果的对比分析,鄂尔多斯块体的周缘壳幔变形符合垂直连贯变形模式,而其内部变形复杂,有待进一步研究.
引文
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4邓起东,程绍平,闵伟,等.鄂尔多斯块体新生代构造活动和动力学的讨论.地质力学学报,1999,3:13-21
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6邓晋福,肖庆辉,邱瑞照,等.华北地区新生代岩石圈伸展减薄的机制与过程.中国地质,2006,33:751-761
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9Chen L,Zheng T Y,Xu W W.Receiver function migration image of the deep structure in the Bohai Bay Basin,eastern China.Geophys Res Lett,2006,33:L20307,doi:10.1029/2006GL027593
10Meissner R,Mooney W D,Artemieva I.Seismic anisotropy and mantle creep in young orogens.Geophys J Int,2002,149:1-14
11高原,郑斯华,周蕙兰.唐山地区快剪切波偏振图像及其变化.地球物理学报,1999,42:228-232
12郑秀芬,陈朝辉,张春贺.1999年台湾集集地震余震区-嘉义地区地震的剪切波分裂参数随时间变化的研究.地球物理学报,2008,51:149-157
13Silver P G,Chan W W.Share-wave splitting and subcontinental mantle deformation.J Geophys Res,1991,96:16429-16454
14郑斯华,高原.中国大陆岩石层的方位各向异性.地震学报,1994,16:131-140
15吕庆田,马开义,姜枚.青藏高原南部下的横波各向异性.地震学报,1996,18:215-223
16丁志峰,曾融生.青藏高原横波分裂的观测研究.地球物理学报,1996,39:211-219
17姜枚,许志琴,Hirn A,等.青藏高原及其部分邻区地震各向异性和上地幔特征.地球学报,2001,22:111-116
18罗艳,黄忠贤,彭艳菊,等.中国大陆及邻区SKS波分裂研究.地球物理学报,2004,47:812-821
19王椿镛,常利军,吕智勇,等.青藏高原东部上地幔各向异性及相关的壳幔耦合型式.中国科学D辑:地球科学,2007,37:495-503
20常利军,王椿镛,丁志峰.云南地区SKS波分裂研究.地球物理学报,2006,49:197-204
21常利军,王椿镛,丁志峰.首都圈地区SKS波分裂研究.地震学报,2008,6:551-559
22Wang L S.Primary results of the upper mantle anisotropy beneath the Western and Southern Ordos,China.AGU Fall Meeting,2006.T51B-1535
23Huang Z C,Xu M J,Wang L X,et al.Shear wave splitting in the southern margin of the Ordos Block,north China.Geophys Res Lett,2008,35:L19301,doi:10.1029/2008GL035188
24Zhao L,Zheng T Y,Lu G.Insight into craton evolution:Constraints from shear wave splitting in the North China Craton.Phys Earth Planet Int,2008,168:153-162
25Liu K H,Gao S S,Gao Y,et al.Shear wave splitting and mantle flow associated with the deflected Pacific slab beneath northeast Asia.J Geophys Res,2008,113:B01305,doi:10.1029/2007JB005178
26常利军,王椿镛,丁志峰,等.青藏高原东北缘上地幔各向异性研究.地球物理学报,2008,51:431-438
27常利军,王椿镛,丁志峰.四川及邻区上地幔各向异性研究.中国科学D辑:地球科学,2008,38:1589-1599
28常利军,王椿镛,丁志峰.中国东部上地幔各向异性研究.中国科学D辑:地球科学,2009,39:1169-1178
29郑秀芬,欧阳飚,张东宁,等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52:1412-1417
30Wolfe C J,Silver P G.Seismic anisotropy of oceanic upper mantle:Shear wave splitting methodologies and observations.J Geophys Res,1998,103(B1):749-771
31马禾青.宁夏地区地壳上地幔各向异性研究.博士学位论文.北京:中国地震局地球物理研究所,2009
32Li S L,Mooney W D,Li H Y.Crustal structure of mainland China from deep seismic sounding data.Tectonophysics,2006,420:239-252
33Silver P G,Kaneshima S,Meade C.Why is the lower mantle so isotropic?Eos Trans AGU,1993,74:313
34Vinnik L P,Makeyeva L I,Milev A,et al.Global patterns of azimuthal anisotropy and deformations in the continental mantle.Geophys J Int,1992,111:433-447
35郝天珧,刘伊克,段昶.中国东部及其邻域地球物理场特征与大地构造意义.地球物理学报,1997,40:677-690
36王涛,徐鸣洁,王良书,等.鄂尔多斯及邻近区航磁异常特征及其大地构造意义.地球物理学报,2007,50:163-170
37An M,Shi Y.Lithospheric thickness of the Chinese continent.Phys Earth Planet Ints,2006,159:257-266
38Gripp A E,Gordon R G.Young tracks of hotspots and current plate velocities.Geophys J Int,2002,150:321-361
39Huang J L,Zhao D P.High-resolution mantle tomography of China and surrounding regions.J Geophys Res,2006,111:B09305,doi:10.1029/2005JB004066
40Silver P G,Savage M K.The interpretation of shear-wave splitting parameters in the presence of two anisotropic layers.Geophys J Int,1994,119:949-963
41Wüstefeld A,Bokelmann G H R,Zaroli C,et al.SplitLab:A shear-wave splitting environment in Matlab.Comput Geosci,2008,34:512-528
42Pei S P,Zhao J M,Sun Y S,et al.Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography.J Geophys Res,2007,112:B05312,doi:10.1029/2006JB004409
43Flesch M L,Holt W E,Silver P G,et al.Constraining the extent of crust-mantle coupling in central Asia using GPS,geologic,and shear wave splitting data.Earth Planet Sci Lett,2005,238:248-268
44Silver P G.Seismic anisotropy beneath the continents:Probing the depths of geology.Annu Rev Earth Planet Sci,1996,24:385-432
45Richardson R M.Ridge forces,absolute plate motions,and the intraplate stress field.J Geophys Res,1992,97:11739-11748
46Wang Q,Zhang P Z,Frevmuller J T,et al.Present-day crustal deformation in China constrained by global positional system measurements.Science,2001,294:574-577
47牛之俊,王敏,孙汉荣,等.中国大陆现今地壳运动速度场的最新观测结果.科学通报,2005,50:839-848
48马宗晋,陈鑫连,叶叔华,等.中国大陆现今地壳运动的GPS研究.科学通报,2001,46:1118-1120
2许忠淮,汪素云,高阿甲.地震活动反映的青藏高原东北地区现代构造运动特征.地震学报,2000,22:472-481
3Zhang Y Q,Mercier J L,Vergely P.Extension in the graben system around the Odors(China),and its contribution to the extrusion tectonics of south China with respect to Gobi-Mongolia.Tectonophysics,1998,285:41-75
4邓起东,程绍平,闵伟,等.鄂尔多斯块体新生代构造活动和动力学的讨论.地质力学学报,1999,3:13-21
5曹井泉.鄂尔多斯块体周缘强震活动时空特征及地震危险性分析.西北地震学报,2002,3:230-235
6邓晋福,肖庆辉,邱瑞照,等.华北地区新生代岩石圈伸展减薄的机制与过程.中国地质,2006,33:751-761
7Griffin W L,Zhang A D,O’Reilly S Y,et al.Phanerozoic evolution of the lithosphere beneath the Sino-Korean Craton.In:Flower M F J,Chung S L,Lo C H,eds.Mantle Dynamics and Plate Interactions in East Asia.Amer Geophys Union Geodyn Ser,1998,27:107-126
8Wu FY,Lin J Q,Wilde S A,et al.Nature and significance of the Early Cretaceous giant igneous event in eastern China.Earth Planet Sci Lett,2005,233:103-119
9Chen L,Zheng T Y,Xu W W.Receiver function migration image of the deep structure in the Bohai Bay Basin,eastern China.Geophys Res Lett,2006,33:L20307,doi:10.1029/2006GL027593
10Meissner R,Mooney W D,Artemieva I.Seismic anisotropy and mantle creep in young orogens.Geophys J Int,2002,149:1-14
11高原,郑斯华,周蕙兰.唐山地区快剪切波偏振图像及其变化.地球物理学报,1999,42:228-232
12郑秀芬,陈朝辉,张春贺.1999年台湾集集地震余震区-嘉义地区地震的剪切波分裂参数随时间变化的研究.地球物理学报,2008,51:149-157
13Silver P G,Chan W W.Share-wave splitting and subcontinental mantle deformation.J Geophys Res,1991,96:16429-16454
14郑斯华,高原.中国大陆岩石层的方位各向异性.地震学报,1994,16:131-140
15吕庆田,马开义,姜枚.青藏高原南部下的横波各向异性.地震学报,1996,18:215-223
16丁志峰,曾融生.青藏高原横波分裂的观测研究.地球物理学报,1996,39:211-219
17姜枚,许志琴,Hirn A,等.青藏高原及其部分邻区地震各向异性和上地幔特征.地球学报,2001,22:111-116
18罗艳,黄忠贤,彭艳菊,等.中国大陆及邻区SKS波分裂研究.地球物理学报,2004,47:812-821
19王椿镛,常利军,吕智勇,等.青藏高原东部上地幔各向异性及相关的壳幔耦合型式.中国科学D辑:地球科学,2007,37:495-503
20常利军,王椿镛,丁志峰.云南地区SKS波分裂研究.地球物理学报,2006,49:197-204
21常利军,王椿镛,丁志峰.首都圈地区SKS波分裂研究.地震学报,2008,6:551-559
22Wang L S.Primary results of the upper mantle anisotropy beneath the Western and Southern Ordos,China.AGU Fall Meeting,2006.T51B-1535
23Huang Z C,Xu M J,Wang L X,et al.Shear wave splitting in the southern margin of the Ordos Block,north China.Geophys Res Lett,2008,35:L19301,doi:10.1029/2008GL035188
24Zhao L,Zheng T Y,Lu G.Insight into craton evolution:Constraints from shear wave splitting in the North China Craton.Phys Earth Planet Int,2008,168:153-162
25Liu K H,Gao S S,Gao Y,et al.Shear wave splitting and mantle flow associated with the deflected Pacific slab beneath northeast Asia.J Geophys Res,2008,113:B01305,doi:10.1029/2007JB005178
26常利军,王椿镛,丁志峰,等.青藏高原东北缘上地幔各向异性研究.地球物理学报,2008,51:431-438
27常利军,王椿镛,丁志峰.四川及邻区上地幔各向异性研究.中国科学D辑:地球科学,2008,38:1589-1599
28常利军,王椿镛,丁志峰.中国东部上地幔各向异性研究.中国科学D辑:地球科学,2009,39:1169-1178
29郑秀芬,欧阳飚,张东宁,等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52:1412-1417
30Wolfe C J,Silver P G.Seismic anisotropy of oceanic upper mantle:Shear wave splitting methodologies and observations.J Geophys Res,1998,103(B1):749-771
31马禾青.宁夏地区地壳上地幔各向异性研究.博士学位论文.北京:中国地震局地球物理研究所,2009
32Li S L,Mooney W D,Li H Y.Crustal structure of mainland China from deep seismic sounding data.Tectonophysics,2006,420:239-252
33Silver P G,Kaneshima S,Meade C.Why is the lower mantle so isotropic?Eos Trans AGU,1993,74:313
34Vinnik L P,Makeyeva L I,Milev A,et al.Global patterns of azimuthal anisotropy and deformations in the continental mantle.Geophys J Int,1992,111:433-447
35郝天珧,刘伊克,段昶.中国东部及其邻域地球物理场特征与大地构造意义.地球物理学报,1997,40:677-690
36王涛,徐鸣洁,王良书,等.鄂尔多斯及邻近区航磁异常特征及其大地构造意义.地球物理学报,2007,50:163-170
37An M,Shi Y.Lithospheric thickness of the Chinese continent.Phys Earth Planet Ints,2006,159:257-266
38Gripp A E,Gordon R G.Young tracks of hotspots and current plate velocities.Geophys J Int,2002,150:321-361
39Huang J L,Zhao D P.High-resolution mantle tomography of China and surrounding regions.J Geophys Res,2006,111:B09305,doi:10.1029/2005JB004066
40Silver P G,Savage M K.The interpretation of shear-wave splitting parameters in the presence of two anisotropic layers.Geophys J Int,1994,119:949-963
41Wüstefeld A,Bokelmann G H R,Zaroli C,et al.SplitLab:A shear-wave splitting environment in Matlab.Comput Geosci,2008,34:512-528
42Pei S P,Zhao J M,Sun Y S,et al.Upper mantle seismic velocities and anisotropy in China determined through Pn and Sn tomography.J Geophys Res,2007,112:B05312,doi:10.1029/2006JB004409
43Flesch M L,Holt W E,Silver P G,et al.Constraining the extent of crust-mantle coupling in central Asia using GPS,geologic,and shear wave splitting data.Earth Planet Sci Lett,2005,238:248-268
44Silver P G.Seismic anisotropy beneath the continents:Probing the depths of geology.Annu Rev Earth Planet Sci,1996,24:385-432
45Richardson R M.Ridge forces,absolute plate motions,and the intraplate stress field.J Geophys Res,1992,97:11739-11748
46Wang Q,Zhang P Z,Frevmuller J T,et al.Present-day crustal deformation in China constrained by global positional system measurements.Science,2001,294:574-577
47牛之俊,王敏,孙汉荣,等.中国大陆现今地壳运动速度场的最新观测结果.科学通报,2005,50:839-848
48马宗晋,陈鑫连,叶叔华,等.中国大陆现今地壳运动的GPS研究.科学通报,2001,46:1118-1120
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