阿尔金断裂带附近地壳结构的接收函数成像及其地球动力学意义
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摘要
利用中法1995年布设在跨过阿尔金断裂剖面上的18个流动三分量地震台站记录到的近5个月的天然地震记录,经筛选得到533个高质量接收函数。通过速度分析和接收函数成像处理,得到了阿尔金断裂附近地壳结构的清晰图像。塔里木盆地的Moho界面非常清楚,近水平地位于~44km深度上。该界面以低缓的角度一直向南延伸到了阿尔金断裂附近的~70km的深度。阿尔金断裂以南柴达木盆地下面的Moho界面也十分清楚,近水平地位于~55km的深度上,在阿尔金断裂附近存在向上挠曲,并抬升到了~45km的深度上。在阿尔金断裂下方,Moho界面存在~15km的错断。塔里木盆地Moho之下还存在另一个震相,我们解释为沉积层多次波与可能来自Hales间断面转换波的复合震相。接收函数成像结果表明阿尔金断裂是一个超壳的岩石圈断裂,具有比较直立的产状和很狭窄的剪切变形带。根据这些结果,我们推测塔里木的下地壳可能要比柴达木的下地壳更硬,柴达木地壳增厚的原因可以部分归结于它有一个相对弱的下地壳,青藏高原隆升没有扩展到塔里木盆地是因为塔里木盆地具有更刚性的下地壳和岩石圈地幔。高原北部地壳变形应该是所谓青藏高原隆升的“硬”变形模式(Tapponnieretal.,2001)和“软”变形模式(EnglandandHouseman,1989;ClarkandRoyden,2000)共同作用的结果。
In the framework of a Sino-French cooperative project 18 three-component portable seismic stations were deployed across the Altyn Tagh fault (ATF) for about five months. From the data recorded on this array, 533 receiver functions with sufficient quality are selected and used in this study. A cross-section about the detailed crustal structures across ATF is then obtained after velocity analysis, common conversion point migration and stacking processes. The Moho discontinuity on the Tarim side is distinctly imaged sub-horizontally at depths of ～44 km. This discontinuity underthrusts gently and smoothly under the Altyn Tagh to a depth of ～70 km beneath ATF. The Moho discontinuity south of ATF is also obvious, and distributed sub-horizontally around ～55 km depth. But, it is heaved up, or “plowed up”, by the Tarim lower crust to a depth of ～45 km near ATF. A fault offset of ～15 km in Moho is seen approximately under the surface trace of ATF. There is an another phase observed ～20 km below the Moho in the Tarim basin, which is interpreted to be the compound energies from the multiple converted phases in the sedimentary layer and the directly converted phases of the Hales discontinuity. Our results indicate that ATF is a lithospheric fault, which extends sub-vertically and characterised by a narrow shear zone. Based on these results, we conclude that the lower crust beneath the Tarim basin is more “hard” than that beneath the Qaidam basin. The thickening of Qaidam crust may be partly ascribed to its more “soft” lower crust. The Tibetan plateau can not grow into the Tarim basin is probably simply because the later has more “hard” lower crust and lithospheric mantle. Our results imply that the mechanism of crustal deformation in the northern-most plateau might have some major features outlined in the “hard Tibet” paradigm (Tapponnier et al., 2001) and but also have some other major characters described in the “soft Tibet” paradigm (England and Houseman, 1989; Clark and Royden, 2000).
In the framework of a Sino-French cooperative project 18 three-component portable seismic stations were deployed across the Altyn Tagh fault (ATF) for about five months. From the data recorded on this array, 533 receiver functions with sufficient quality are selected and used in this study. A cross-section about the detailed crustal structures across ATF is then obtained after velocity analysis, common conversion point migration and stacking processes. The Moho discontinuity on the Tarim side is distinctly imaged sub-horizontally at depths of ～44 km. This discontinuity underthrusts gently and smoothly under the Altyn Tagh to a depth of ～70 km beneath ATF. The Moho discontinuity south of ATF is also obvious, and distributed sub-horizontally around ～55 km depth. But, it is heaved up, or “plowed up”, by the Tarim lower crust to a depth of ～45 km near ATF. A fault offset of ～15 km in Moho is seen approximately under the surface trace of ATF. There is an another phase observed ～20 km below the Moho in the Tarim basin, which is interpreted to be the compound energies from the multiple converted phases in the sedimentary layer and the directly converted phases of the Hales discontinuity. Our results indicate that ATF is a lithospheric fault, which extends sub-vertically and characterised by a narrow shear zone. Based on these results, we conclude that the lower crust beneath the Tarim basin is more “hard” than that beneath the Qaidam basin. The thickening of Qaidam crust may be partly ascribed to its more “soft” lower crust. The Tibetan plateau can not grow into the Tarim basin is probably simply because the later has more “hard” lower crust and lithospheric mantle. Our results imply that the mechanism of crustal deformation in the northern-most plateau might have some major features outlined in the “hard Tibet” paradigm (Tapponnier et al., 2001) and but also have some other major characters described in the “soft Tibet” paradigm (England and Houseman, 1989; Clark and Royden, 2000).
引文
史大年,姜枚,马开义,薛光琦,董英君,Poupinet G,Wittlinger G,Herauel G.1999.阿尔金断裂带地壳和上地幔结构的P波层析成像.地球物理学报,42(3):341~350.
刘启元,陈九辉,李顺成,郭飚.2000.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,43(3):356~365.
汤良杰.1996.塔里木盆地演化和构造式样.地质出版社.
汤良杰,张一伟,金之钧,贾承造.2004.塔里木盆地、柴达木盆地的开合旋回.地质通报,23(3):254~260.
姜春发,杨经绥,冯秉贵.1992.昆仑开合构造.地质出版社.
崔军文,唐哲民,邓晋福,岳永君,孟令顺,余钦范.1999.阿尔金断裂系.地质出版社.
Ammon C J.1991.The isolation of receiver effects from teleseismic Pwaveforms.Bulletin of the Seismological Society of America,81:2504~2510.
Ammon C J,Randall G E,and Zandt G.1990.On the nonuniquenessof receiver function inversions.J.Geophys.Res.,95(B10):150~15318.
Beaumont C,Jamieson R A,Nguyen M H,and Lee B.2001.Himalayan tectonics explained by extrusion of a low-viscositycrustal channel coupled to focused surface denudation.Nature,414:738~742.
Bendick R,Bilham R,Freymueller J,Larson K,and Yin G.2000.Geodetic evidence for a low slip rate in the Altyn Tagh faultsystem.Nature,404:69~72.
Bostock M G,and Rondenay S.1999.Migration of scatteredteleseismic body waves.Geophysical Journal International,137:732~746.
Bostock M G.1998.Seismic stratigraphy and evolution of the Slaveprovince.Journal of Geophysical Research,103:21183~21200.
Bostock M G,Rondenay S,and Shragge J.2001.Multiparametertwo-dimensional inversion of scattered teleseismic body waves,1,Theory for oblique incidence.J.Geophys.Res.,106:30771~30782.
Clark M K,and Royden L H.2000.Topographic ooze;building theeastern margin of Tibet by lower crustal flow.Geology,28:703~706.
England P C,and Houseman G A.1989.Extension during continentalconvergence,with application to the Tibetan plateau.Journal ofGeophysical Research,94:17561~17579.
Kao H,Gao Rui,Rau Ruey Juin,Shi Danian,Chen Rong Yuh,GuanYe,and Wu Francis T.2001.Seismic image of the Tarim basinand its collision with Tibet.Geology,29(7):575~578.
Hales A L,1969.A seismic discontinuity in the lithosphere.EarthPlanet.Sci.Lett.,7:44~46.
Hirn A C.1975.Prodehl and L.Steinmetz,An experimental test ofmodels of the lower lithosphere in Bretagne(France).AnnalesGeophysicae,31:517~530.
Jiang X,Yu Jin,McNutt M K.2004.Lithospheric deformationbeneath the Altyn Tagh and West Kunlun faults from recentgravity surveys.J.Geophys.Res.,109(B05406):doi:10.1029/2003JB002444.
Jin Y,McNutt M,and Zhu Y.1996.Mapping the descent of Indianand Eurasian plates beneath the Tibetan Plateau from gravityanomalies.J.Geophys.Res.,101:11275~11290.
Kind R,Yuan X,Saul J,Nelson D,Sobolev S V,Mechie J,Zhao W,Kosarev G,Ni J,Achauer U,and Jiang M.2002.SeismicImages of the Crust and Upper Mantle beneath Tibet:EvidenceFor Eurasian Plate Subduction.Science,298:1219~1211.
Klemperer S L.2006.Crustal flow in Tibet:a review of geophysicalevidence for the physical state of Tibetan lithosphere.In:"Channel flow,ductile extrusion and exhumation of lower mid-crust in continental collision zones,eds.M.P.Searle,R.D.Lawand L.Godin,Geological Society of London Special Publication.
Kosarev G,Kind R,Sobolev S V,Yuan X,Hanka W,Oreshin S.1999.Seismic evidence for a detached Indian lithospheric mantlebeneath Tibet.Science,283:1306~1309.
Langston C A.1979.Structure under Mount Rainier,Washington,Inferred from Teleseismic body waves.J.Geophys.Res.,84:4749~4762.
Levin V,and Park J.2000.Shear zones in the Proterozoic lithosphereof the Arabian Shield and the nature of the Hales discontinuity.Tectonophysics,323:131~148.
Li D,Liang D,Jia C,Wang G,Wu Q,and He D.1996.Hydrocarbon accumulations in the Tarim basin,China.Am.Assoc.Pet.Geol.Bull.,80:1587~1603.
Molnar P,Buchfiel B C,Liang K,Zhao Z.1987.Geomorphicevidence for active faulting in the Altyn Tagh and northern Tibetand qualitative estimates of contribution to the convergence ofIndian and Eurasia.Geology,15:249~253.
Nabelek J L,Li X Q,Azevedo S,Braunmiller J,Fabritius A,LeitnerB,and Trehu A.1993.A high-resolution image of the Cascadiasubduction zone from teleseismic converted phases recorded by abroadband seismic array(Abstract).EOS Trans.Am.Geophys.Union,74:s42.
Owens T J,Zandt G,and Taylor S R.1984.Seismic evidence for anAncient Rift beneath the Cumberland Plateau,Tennessee:Adetailed analysis of broadband teleseismic P waveforms.J.Geophys.Res.,89(B9):7783~7795.
Owens T J,Taylor S R,and Zandt G.1987.Crustal structure atregional seismic test network stations determined from inversionof broadband teleseismic P waveforms.Bull.Seismol.Soc.Am.,77:631~632.
Peltzer G,Tapponnier P,Armijo R.1989.Magnitude of lateQuaternary left-lateral displacements along the northern edge ofTibet.Science,246:1285~1289.
Phinney R A.1964.Structure of the Earth's crust from spectralbehavior of long-period body waves.J.Geophys.Res.,69:2997~107.
Shi Danian,Zhao Wenjin,Brown L,Nelson D,Zhao Xun,Kind R,Ni J,Xiong Jiayu,Mechie J,Guo Jinru,Klemperer S,Hearn T.2004.Detection of southward intracontinental subduction ofTibetan lithosphere along the Bangong-Nujiang suture by P-to-Sconverted waves.Geology,32(3):209~212.
Tapponnier P,and Molnar P.1977.Active tectonics and faulting oChina.J.Geophys.Res.,82:2905~2930.
Tapponnier P,Xu Z,Roger F,Meyer B,Arnaud N,Wittlinger G,Yang J.2001.Oblique stepwise rise and growth of the Tibetplateau.Sciences,294:1671~1677.
Wang Youxue,Mooney W D,Yuan Xuecheng,Coleman R G.2003.The crustal structure from the Altai Mountains to the Altyn Taghfault,northwest China.J.Geophys.Res.,108(B6):ESE7-1,CiteID2322,DOI10.1029/2001JB000552.
Wittlinger G,Tapponnier P,Poupinet G,Jiang Mei,Shi Danian,Herquel G,Masson F.1998.Tomographic evidence for localizedlithospheric shear along the altyn tagh fault.Science,282:74~76.
Wittlinger G,Vergne J,Tapponnier P,Farra V,Poupinet G,JiangM,Su H,Herquel G,and Paul A.2004.Teleseismic imaging ofsubducting lithosphere and Moho offsets beneath western Tibet.Earth Planet.Sci.Lett.,221:117~130.
Yin A,and Harrison T M.2000.Geological evolution of theHimalayan-Tibetan orogen.J.Ann.Rev.Earth Planet Sci.,28:211~280.
Zhao W,Nelson K D,and Project INDEPTH Team.1993.Deepseismic reflection evidence for continental underthrusting beneathsouthern Tibet.Nature,366:557~559.
Zhu Lupei,and Helmberger D V.1996.Intermediate DepthEarthquakes beneath the India-Tibet Collision Zone.Geophys.Res.Lett.,23(5),435~438.
刘启元,陈九辉,李顺成,郭飚.2000.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,43(3):356~365.
汤良杰.1996.塔里木盆地演化和构造式样.地质出版社.
汤良杰,张一伟,金之钧,贾承造.2004.塔里木盆地、柴达木盆地的开合旋回.地质通报,23(3):254~260.
姜春发,杨经绥,冯秉贵.1992.昆仑开合构造.地质出版社.
崔军文,唐哲民,邓晋福,岳永君,孟令顺,余钦范.1999.阿尔金断裂系.地质出版社.
Ammon C J.1991.The isolation of receiver effects from teleseismic Pwaveforms.Bulletin of the Seismological Society of America,81:2504~2510.
Ammon C J,Randall G E,and Zandt G.1990.On the nonuniquenessof receiver function inversions.J.Geophys.Res.,95(B10):150~15318.
Beaumont C,Jamieson R A,Nguyen M H,and Lee B.2001.Himalayan tectonics explained by extrusion of a low-viscositycrustal channel coupled to focused surface denudation.Nature,414:738~742.
Bendick R,Bilham R,Freymueller J,Larson K,and Yin G.2000.Geodetic evidence for a low slip rate in the Altyn Tagh faultsystem.Nature,404:69~72.
Bostock M G,and Rondenay S.1999.Migration of scatteredteleseismic body waves.Geophysical Journal International,137:732~746.
Bostock M G.1998.Seismic stratigraphy and evolution of the Slaveprovince.Journal of Geophysical Research,103:21183~21200.
Bostock M G,Rondenay S,and Shragge J.2001.Multiparametertwo-dimensional inversion of scattered teleseismic body waves,1,Theory for oblique incidence.J.Geophys.Res.,106:30771~30782.
Clark M K,and Royden L H.2000.Topographic ooze;building theeastern margin of Tibet by lower crustal flow.Geology,28:703~706.
England P C,and Houseman G A.1989.Extension during continentalconvergence,with application to the Tibetan plateau.Journal ofGeophysical Research,94:17561~17579.
Kao H,Gao Rui,Rau Ruey Juin,Shi Danian,Chen Rong Yuh,GuanYe,and Wu Francis T.2001.Seismic image of the Tarim basinand its collision with Tibet.Geology,29(7):575~578.
Hales A L,1969.A seismic discontinuity in the lithosphere.EarthPlanet.Sci.Lett.,7:44~46.
Hirn A C.1975.Prodehl and L.Steinmetz,An experimental test ofmodels of the lower lithosphere in Bretagne(France).AnnalesGeophysicae,31:517~530.
Jiang X,Yu Jin,McNutt M K.2004.Lithospheric deformationbeneath the Altyn Tagh and West Kunlun faults from recentgravity surveys.J.Geophys.Res.,109(B05406):doi:10.1029/2003JB002444.
Jin Y,McNutt M,and Zhu Y.1996.Mapping the descent of Indianand Eurasian plates beneath the Tibetan Plateau from gravityanomalies.J.Geophys.Res.,101:11275~11290.
Kind R,Yuan X,Saul J,Nelson D,Sobolev S V,Mechie J,Zhao W,Kosarev G,Ni J,Achauer U,and Jiang M.2002.SeismicImages of the Crust and Upper Mantle beneath Tibet:EvidenceFor Eurasian Plate Subduction.Science,298:1219~1211.
Klemperer S L.2006.Crustal flow in Tibet:a review of geophysicalevidence for the physical state of Tibetan lithosphere.In:"Channel flow,ductile extrusion and exhumation of lower mid-crust in continental collision zones,eds.M.P.Searle,R.D.Lawand L.Godin,Geological Society of London Special Publication.
Kosarev G,Kind R,Sobolev S V,Yuan X,Hanka W,Oreshin S.1999.Seismic evidence for a detached Indian lithospheric mantlebeneath Tibet.Science,283:1306~1309.
Langston C A.1979.Structure under Mount Rainier,Washington,Inferred from Teleseismic body waves.J.Geophys.Res.,84:4749~4762.
Levin V,and Park J.2000.Shear zones in the Proterozoic lithosphereof the Arabian Shield and the nature of the Hales discontinuity.Tectonophysics,323:131~148.
Li D,Liang D,Jia C,Wang G,Wu Q,and He D.1996.Hydrocarbon accumulations in the Tarim basin,China.Am.Assoc.Pet.Geol.Bull.,80:1587~1603.
Molnar P,Buchfiel B C,Liang K,Zhao Z.1987.Geomorphicevidence for active faulting in the Altyn Tagh and northern Tibetand qualitative estimates of contribution to the convergence ofIndian and Eurasia.Geology,15:249~253.
Nabelek J L,Li X Q,Azevedo S,Braunmiller J,Fabritius A,LeitnerB,and Trehu A.1993.A high-resolution image of the Cascadiasubduction zone from teleseismic converted phases recorded by abroadband seismic array(Abstract).EOS Trans.Am.Geophys.Union,74:s42.
Owens T J,Zandt G,and Taylor S R.1984.Seismic evidence for anAncient Rift beneath the Cumberland Plateau,Tennessee:Adetailed analysis of broadband teleseismic P waveforms.J.Geophys.Res.,89(B9):7783~7795.
Owens T J,Taylor S R,and Zandt G.1987.Crustal structure atregional seismic test network stations determined from inversionof broadband teleseismic P waveforms.Bull.Seismol.Soc.Am.,77:631~632.
Peltzer G,Tapponnier P,Armijo R.1989.Magnitude of lateQuaternary left-lateral displacements along the northern edge ofTibet.Science,246:1285~1289.
Phinney R A.1964.Structure of the Earth's crust from spectralbehavior of long-period body waves.J.Geophys.Res.,69:2997~107.
Shi Danian,Zhao Wenjin,Brown L,Nelson D,Zhao Xun,Kind R,Ni J,Xiong Jiayu,Mechie J,Guo Jinru,Klemperer S,Hearn T.2004.Detection of southward intracontinental subduction ofTibetan lithosphere along the Bangong-Nujiang suture by P-to-Sconverted waves.Geology,32(3):209~212.
Tapponnier P,and Molnar P.1977.Active tectonics and faulting oChina.J.Geophys.Res.,82:2905~2930.
Tapponnier P,Xu Z,Roger F,Meyer B,Arnaud N,Wittlinger G,Yang J.2001.Oblique stepwise rise and growth of the Tibetplateau.Sciences,294:1671~1677.
Wang Youxue,Mooney W D,Yuan Xuecheng,Coleman R G.2003.The crustal structure from the Altai Mountains to the Altyn Taghfault,northwest China.J.Geophys.Res.,108(B6):ESE7-1,CiteID2322,DOI10.1029/2001JB000552.
Wittlinger G,Tapponnier P,Poupinet G,Jiang Mei,Shi Danian,Herquel G,Masson F.1998.Tomographic evidence for localizedlithospheric shear along the altyn tagh fault.Science,282:74~76.
Wittlinger G,Vergne J,Tapponnier P,Farra V,Poupinet G,JiangM,Su H,Herquel G,and Paul A.2004.Teleseismic imaging ofsubducting lithosphere and Moho offsets beneath western Tibet.Earth Planet.Sci.Lett.,221:117~130.
Yin A,and Harrison T M.2000.Geological evolution of theHimalayan-Tibetan orogen.J.Ann.Rev.Earth Planet Sci.,28:211~280.
Zhao W,Nelson K D,and Project INDEPTH Team.1993.Deepseismic reflection evidence for continental underthrusting beneathsouthern Tibet.Nature,366:557~559.
Zhu Lupei,and Helmberger D V.1996.Intermediate DepthEarthquakes beneath the India-Tibet Collision Zone.Geophys.Res.Lett.,23(5),435~438.
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