印度板块岩石圈地幔向北俯冲到羌塘地体之下的远震P波层析成像证据
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摘要
利用PASSCALI、NDEPTH-ⅡI、NDEPTH-Ⅲ、HIMNT等研究计划,及中国新疆地学断面和国家973项目在青藏高原布设的流动台站记录的到时数据,以及自1990年1月到2004年2月全球地震事件的震相报告,作者对覆盖印度大陆的恒河平原和整个青藏高原的305个地震台站记录的9649个远震事件,共139021条P波初至到时资料进行了层析成像反演.结果表明:印度岩石圈地幔在不同的位置向北俯冲的形态不同,但俯冲前缘都到达羌塘地体之下.沿88°E剖面显示,厚约100 km的印度岩石圈地幔从南部的恒河平原向北一直俯冲到青藏高原之下.在主边界逆冲断裂之下100 km深度处以约22°角度开始向北俯冲,俯冲最前缘到达羌塘地体的中部地区约34°N,之后进入上地幔深处.而沿北东方向的剖面则显示,印度岩石圈地幔以近水平的角度俯冲到青藏高原之下,向北越过班公-怒江缝合带,到达33°N附近,然后以大角度近乎垂直地向下俯冲断离,并引起地幔热物质的上涌,形成羌塘地体之下大规模的低速带.
We have collected all the available arrival time data recorded by the temporary seismic stations from the projects of PASSCAL,INDEPTH-Ⅱ,INDEPTHⅢ, HIMNT,WKL and TIBET 973,and phase reports from the International Seismological Center from January 1990 to February 2004 in Tibet and its surrounding areas.In the tomographic inversion,we have used 139021 P-wave arrival times from 9649 teleseismic events recorded by 305 seismic stations.Our study area covers the southern Ganges plain in India to the northern Tarim basin and Qaidam basin in China.Our tomographic images show that the subducting angles of Indian lithospheric mantle are different under different areas,but their front locations are all beneath the Qiangtang terrane.The tomographic images along 88°E show that the Indian lithospheric mantle is underthrusting northward with a dip angle of about 22° beneath the center of Qiangtang terrane at about 34°N latitude,and its frontier has reached to the deep part of the upper mantle.The tomographic images along a northeasterly profile show that the Indian mantle has nearly horizontally underthrust under the Tibet from Ganges plain to 33°N.Then,the Indian mantle broke off down to the asthenosphere and caused the asthenophere upwelling.A consequence of the asthenophere upwelling was to form a big low-velocity zone beneath the Qiangtang terrane.
We have collected all the available arrival time data recorded by the temporary seismic stations from the projects of PASSCAL,INDEPTH-Ⅱ,INDEPTHⅢ, HIMNT,WKL and TIBET 973,and phase reports from the International Seismological Center from January 1990 to February 2004 in Tibet and its surrounding areas.In the tomographic inversion,we have used 139021 P-wave arrival times from 9649 teleseismic events recorded by 305 seismic stations.Our study area covers the southern Ganges plain in India to the northern Tarim basin and Qaidam basin in China.Our tomographic images show that the subducting angles of Indian lithospheric mantle are different under different areas,but their front locations are all beneath the Qiangtang terrane.The tomographic images along 88°E show that the Indian lithospheric mantle is underthrusting northward with a dip angle of about 22° beneath the center of Qiangtang terrane at about 34°N latitude,and its frontier has reached to the deep part of the upper mantle.The tomographic images along a northeasterly profile show that the Indian mantle has nearly horizontally underthrust under the Tibet from Ganges plain to 33°N.Then,the Indian mantle broke off down to the asthenosphere and caused the asthenophere upwelling.A consequence of the asthenophere upwelling was to form a big low-velocity zone beneath the Qiangtang terrane.
引文
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[15]Unsworth M J,Jones A G,Wei W,et al.Crustal rheology of theHimalaya and southern Tibet inferred from magnetotelluric data.Nature,2005,438(3):78~81
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[17]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath northeastern Japan.J.Geophys.Res.,1992,97:19909~19928
[18]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japan subductionzone as derived from local,regional,and teleseismic events.J.Geophys.Res.,1994,99(B11):22313~22329
[19]Um J,Thurber C H.A fast algorithm for two-point seismic ray tracing.Bull.Seismol.Soc.Am.,1987,77:972~986
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[22]Molnar P.A review of geophysical constraints on the deep structure ofthe Tibetan plateau,the Himalaya and the Karakoram,and theirtectonic implications.Phil.Trans.R.Soc.Lond.,1988,A326:33~88
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[24]Owens T J,Zandt G.Implications of crustal property variations formodels of Tibetan plateau evolution.Nature,1997,387:37~43
[25]谭捍东,魏文博,Unsworth M J等.西藏高原南部雅鲁藏布江缝合带地区地壳电性结构研究.地球物理学报,2004,47(4):685~690Tan H D,Wei W B,Unsworth M J,et al.Crustal electricalconductivity structure beneath the Yarlung Zangbo Jiang suture in thesouthern Xizang plateau.Chinese J.Geophys.(in Chinese),2004,47(4):685~690
[26]薛光琦,宿和平,钱辉等.地震层析对印度板块向北俯冲的认识.地质学报,2006,80(8):1156~1160Xue G Q,Su H P,Qian H,et al.Seismic tomographic constraint onthe northward subduction of the Indian Plate.Acta Geol.Sinica(inChinese),2006,80(8):1156~1160
[27]Beaumont C,Jamieson R A,Nguyen M H,et al.Himalayan tectonicsexplained by extrusion of a low-viscosity crustal channel coupled tofocused surface denudation.Nature,2001,414:738~742
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[29]Wittlinger G,Masson F,Poupinet G,et al.Seismic tomography ofnorthen Tibet and Kunlun:Evidence for crustal blocks and mantlevelocity contrasts.Earth Planet.Sci.Lett.,1996,139:263~276
[30]周华伟,Murphy A M,林清良.西藏及其周围地区地壳、地幔层析成像———印度板块大规模俯冲于西藏高原之下的证据.地学前缘,2002,9(4):285~292Zhou H W,Murphy A M,Lin Q L.Tomographic imaging of the Tibetand surrounding region:Evidence for wholesale underthrusting ofIndian slab beneath the Tibetan plateau.Earth Sci.Fron.(inChinese),2002,9(4):285~292
[31]McNamara D E,Owens T J,Walter W R.Observations of the regionalphase propagation in the Tibetan plateau.J.Geophys.Res.,1995,100:22215~22229
[32]Ding L,Kapp P,Zhong D L,et al.Cenozoic volcanism in Tibet:evidence for a transition from oceanic to continental subduction.J.Petrol.,2003,44(10):1833~1865
[33]邓万明.青藏及邻区新生代火山活动及构造演化.地震地质,2003,25(增刊):51~61Deng W M.Cenozoic volcanism and tectonic evolution in the Tibetanplateau and its adjace areas.Seismol.Geol.(in Chinese),2003,25(Suppl.):51~61
[34]赖绍聪.青藏高原新生代三阶段造山隆升模式:火成岩岩石学约束.矿物学报,2000,20(2):182~190Lai S C.Three-phase uplifting model of Qinghai-Tibet plateau duringCenozoic:Igneous petrology constraints.Acta Mineral.Sinica(inChinese),2000,20(2):182~190
[35]罗照华,肖序常,曹永清等.青藏高原北缘新生代幔源岩浆活动及构造运动性质.中国科学(D辑),2003,31(增刊):8~13Luo Z H,Xiao X C,Cao Y Q,et al.Cenozic mantle-derivedmagmatism activity and tectonic kinematic property in the northernmargin of the Tibetan plateau.Sci.China(Series D)(in Chinese),2003,31(Suppl.):8~13
[36]Humphreys E R,Clayton R W.Adaptation of back projectiontomography to seismic travel time problems.J.Geophys.Res.,1988,93:1073~1085
[37]齐诚.中国首都圈和美国阿拉斯加地区的地震层析成像研究[博士论文].北京:中国科学院研究生院,2006Qi C.Seismic tomography and dynamics of the Chinese capital regionand the Alaska subduction zone[Ph.D.thesis](in Chinese).Beijing:Graduate University of Chinese Academy of Sciences,2006
[38]Zhao Z,Mo X,Depaolo D J,et al.Postcollisional potassic andultrapotassic volcanic rocks in southern Tibet:Geochemistry andimplications for the subduction of Indian plate.Abstract Volume of the18 th Himalaya-Karakoram-Tibet Workshop(HKTW),2003.136
[39]Tapponnier P,Xu Z Q,Roger F,et al.Oblique stepwise rise andgrowth of the Tibet plateau.Science,2001,294:1671~1677
[40]Wessel P,Smith W.New version of the generic mapping tools(GMT)version 3.0 released.EOS Trans.AGU,1995,76:329
[2]Ni J,Barazangi M.Seismotectonics of the Himalayan collision zone:Geometry of the underthrusting Indian plate beneath the Himalayan.J.Geophys.Res.,1984,89:1147~1163
[3]Zhou H,Murphy M A.Tomographic evidence for wholesaleunderthrusting of India beneath the entire Tibetan plateau.J.AsianEarth Sci.,2005,25:445~457
[4]朱介寿,蔡学林,曹家敏等.中国及相邻区域岩石圈结构及动力学意义.中国地质,2006,33(4):793~803Zhu J S,Cai X L,Cao J M,et al.Lithospheric structure andgeodynamics in China and its adjacent areas.Geol.China(inChinese),2006,33(4):793~803
[5]Jin Y,Mcnutt M K,Zhu Y.Mapping the descent of Indian andEurasian plates beneath the Tibetan plateau from gravity anomalies.J.Geophys.Res.,1996,101(B5):11275~11290
[6]Tilmann F,Ni J,INDEPTH-ⅢSeismic Team.Seismic imaging of thedownwelling Indian lithosphere beneath central Tibet.Science,2003,300:1424~1427
[7]Chung S L,Chu M F,Zhang Y,et al.Tibetan tectonic evolutioninferred from spatial and temporal variations in post-collisionalmagmatism.Earth-Science Reviews,2005,68:173~196
[8]Kosarev G,Kind R,Sobolev SV,et al.Seismic evidence for a detachedIndian lithospheric mantle beneath Tibet.Science,1999,283:1306~1309
[9]Kind R,Yuan X,Saul J,et al.Seismic images of crust and uppermantle beneath Tibet:Evidence for Eurasian plate subduction.Science,2002,298:1219~1221
[10]魏文博,陈乐寿,谭捍东等.关于印度板块俯冲的探讨—据INDEPTH-MT研究结果.现代地质,1997,11(3):379~386Wei W B,Chen L S,Tan H D,et al.An approach on subduction ofIndian plate from INDEPTH-MT result.Geoscience(in Chinese),1997,11(3):379~386
[11]丁志峰,曾融生,吴大铭.青藏高原的Pn波速度和Moho界面的起伏.地震学报,1992,14(增刊):592~599Ding Z F,Zeng R S,Wu D M.The Pn wave velocity and the relief ofMoho in the Tibetan plateau.Acta Seismol.Sinica(in Chinese),1992,14(Suppl.):592~599
[12]吴建平,明跃红,叶太兰等.体波波形反演对青藏高原上地幔速度结构的研究.地球物理学报,1998,41(增刊):15~25Wu J P,Ming Y H,Ye T L,et al.Upper mantle velocity structure inthe Qianghai-Xizang plateau from inversion of body waveforms.Chinese J.Geophys.(in Chinese),1998,41(Suppl.):15~25
[13]吕庆田,姜枚,许志琴等.印度板块俯冲仅到特提斯喜马拉雅之下的地震层析证据.科学通报,1998,43(12):1308~1311LüQ T,Jiang M,Xu Z Q,et al.Tomography evidence for India plateunderthrusting only beneath Tethyan Himalaya.Chinese Sci.Bull.(inChinese),1998,43(12):1308~1311
[14]Nelson K D,Zhao W J,Brown L D,et al.Partially molten middle crustbeneath southern Tibet:synthesis of project INDEPTH results.Science,1996,274:1684~1687
[15]Unsworth M J,Jones A G,Wei W,et al.Crustal rheology of theHimalaya and southern Tibet inferred from magnetotelluric data.Nature,2005,438(3):78~81
[16]侯增谦,李振清.印度大陆俯冲前缘的可能位置:来自藏南和藏东活动热泉气体He同位素约束.地质学报,2004,4:482~493Hou Z Q,Li Z Q.Possible location for underthrusting front of theIndus Continent constraints from Helium isotope of the geothermal gasin southern Tibet and eastern Tibet.Acta Geol.Sinica(in Chinese),2004,4:482~493
[17]Zhao D,Hasegawa A,Horiuchi S.Tomographic imaging of P and Swave velocity structure beneath northeastern Japan.J.Geophys.Res.,1992,97:19909~19928
[18]Zhao D,Hasegawa A,Kanamori H.Deep structure of Japan subductionzone as derived from local,regional,and teleseismic events.J.Geophys.Res.,1994,99(B11):22313~22329
[19]Um J,Thurber C H.A fast algorithm for two-point seismic ray tracing.Bull.Seismol.Soc.Am.,1987,77:972~986
[20]Paige C C,Saunders M A.LSQR:An algorithm for sparse linearequations and sparse least squares.Assoc.Comput.Mach.Trans.Math.Soferware,1982,8:43~71
[21]Dewey J F,Shackleton R M,Chang C F,et al.The tectonic evolutionof the Tibetan.Phil.Trans.R.Soc.Lond.,1988,327:379~413
[22]Molnar P.A review of geophysical constraints on the deep structure ofthe Tibetan plateau,the Himalaya and the Karakoram,and theirtectonic implications.Phil.Trans.R.Soc.Lond.,1988,A326:33~88
[23]赵文津,薛光琦,吴珍汉等.西藏高原上地幔的精细结构与构造-地震层析成像给出的启示.地球物理学报,2004,47(3):449~458Zhao W J,Xue G Q,Wu Z H,et al.Fine velocity structure of theupper mantle beneath the Xizang plateau from tomography and itsgeological interpretations.Chinese J.Geophys.(in Chinese),2004,47(3):449~458
[24]Owens T J,Zandt G.Implications of crustal property variations formodels of Tibetan plateau evolution.Nature,1997,387:37~43
[25]谭捍东,魏文博,Unsworth M J等.西藏高原南部雅鲁藏布江缝合带地区地壳电性结构研究.地球物理学报,2004,47(4):685~690Tan H D,Wei W B,Unsworth M J,et al.Crustal electricalconductivity structure beneath the Yarlung Zangbo Jiang suture in thesouthern Xizang plateau.Chinese J.Geophys.(in Chinese),2004,47(4):685~690
[26]薛光琦,宿和平,钱辉等.地震层析对印度板块向北俯冲的认识.地质学报,2006,80(8):1156~1160Xue G Q,Su H P,Qian H,et al.Seismic tomographic constraint onthe northward subduction of the Indian Plate.Acta Geol.Sinica(inChinese),2006,80(8):1156~1160
[27]Beaumont C,Jamieson R A,Nguyen M H,et al.Himalayan tectonicsexplained by extrusion of a low-viscosity crustal channel coupled tofocused surface denudation.Nature,2001,414:738~742
[28]崔作舟,尹周勋,高恩元等.青藏高原地壳结构及其与地震的关系.中国地质科学院院报,1990,21:215~225Cui Z Z,Yin Z X,Gao E Y,et al.The crust structure and its relationsto seismic in Qinghai-Tibet plateau.Bull.Chinese Acad.Geol.Sci.,1990,21:215~225
[29]Wittlinger G,Masson F,Poupinet G,et al.Seismic tomography ofnorthen Tibet and Kunlun:Evidence for crustal blocks and mantlevelocity contrasts.Earth Planet.Sci.Lett.,1996,139:263~276
[30]周华伟,Murphy A M,林清良.西藏及其周围地区地壳、地幔层析成像———印度板块大规模俯冲于西藏高原之下的证据.地学前缘,2002,9(4):285~292Zhou H W,Murphy A M,Lin Q L.Tomographic imaging of the Tibetand surrounding region:Evidence for wholesale underthrusting ofIndian slab beneath the Tibetan plateau.Earth Sci.Fron.(inChinese),2002,9(4):285~292
[31]McNamara D E,Owens T J,Walter W R.Observations of the regionalphase propagation in the Tibetan plateau.J.Geophys.Res.,1995,100:22215~22229
[32]Ding L,Kapp P,Zhong D L,et al.Cenozoic volcanism in Tibet:evidence for a transition from oceanic to continental subduction.J.Petrol.,2003,44(10):1833~1865
[33]邓万明.青藏及邻区新生代火山活动及构造演化.地震地质,2003,25(增刊):51~61Deng W M.Cenozoic volcanism and tectonic evolution in the Tibetanplateau and its adjace areas.Seismol.Geol.(in Chinese),2003,25(Suppl.):51~61
[34]赖绍聪.青藏高原新生代三阶段造山隆升模式:火成岩岩石学约束.矿物学报,2000,20(2):182~190Lai S C.Three-phase uplifting model of Qinghai-Tibet plateau duringCenozoic:Igneous petrology constraints.Acta Mineral.Sinica(inChinese),2000,20(2):182~190
[35]罗照华,肖序常,曹永清等.青藏高原北缘新生代幔源岩浆活动及构造运动性质.中国科学(D辑),2003,31(增刊):8~13Luo Z H,Xiao X C,Cao Y Q,et al.Cenozic mantle-derivedmagmatism activity and tectonic kinematic property in the northernmargin of the Tibetan plateau.Sci.China(Series D)(in Chinese),2003,31(Suppl.):8~13
[36]Humphreys E R,Clayton R W.Adaptation of back projectiontomography to seismic travel time problems.J.Geophys.Res.,1988,93:1073~1085
[37]齐诚.中国首都圈和美国阿拉斯加地区的地震层析成像研究[博士论文].北京:中国科学院研究生院,2006Qi C.Seismic tomography and dynamics of the Chinese capital regionand the Alaska subduction zone[Ph.D.thesis](in Chinese).Beijing:Graduate University of Chinese Academy of Sciences,2006
[38]Zhao Z,Mo X,Depaolo D J,et al.Postcollisional potassic andultrapotassic volcanic rocks in southern Tibet:Geochemistry andimplications for the subduction of Indian plate.Abstract Volume of the18 th Himalaya-Karakoram-Tibet Workshop(HKTW),2003.136
[39]Tapponnier P,Xu Z Q,Roger F,et al.Oblique stepwise rise andgrowth of the Tibet plateau.Science,2001,294:1671~1677
[40]Wessel P,Smith W.New version of the generic mapping tools(GMT)version 3.0 released.EOS Trans.AGU,1995,76:329
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