藏北低速体存在的地震学证据——INDEPTH4宽频地震结果
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摘要
位于青藏高原东北部的INDEPTH-IV地震探测剖面,始于柴达木盆地南缘,穿越东昆仑造山带、金沙江缝合线,终止于羌塘地体。本文作者利用天然地震体波完成了该区的三维走时残差反演,勾划出了青藏高原东北部的深部构造格局。研究区最显著的现象则是分布在昆仑地体、可可西里地体、羌塘地体北部下地壳、上地幔中的低速体。对其成因,有可能与向北俯冲的印度板片与向南俯冲的欧亚板片在此聚合形成的地幔热物质有关。另外,昆南、昆中断裂、金沙江断裂向南的逆冲现象比较明显;推测柴达木盆地的上地幔中没有热物质的交流,为刚性岩石圈。
The INDEPTH-IV seismic profile,located in northeastern Qinghai-Tibetan Plateau,starts at the north end of Qaidam Basin,extends across East Kunlun Fault Zone,Jinsha Suture,and ends at Qiangtang Terrain.The authors implemented a 3-D travel-time residual reversion using body-wave from the natural earthquake,and outlined the pattern of the deep-seated structure underneath the northeast part of the Qinghai-Tibetan Plateau.The most notable phenomenon in the area of interest is the existence of low-velocity bodies distributed between the lower-crust and the upper-mantle beneath the Kunlun Terrain,Hoh Xil Terrain and the north part of Qiangtang Terrain,probably related to the hot mantle material derived from the collision between the northward thrusting Indian Plate and southward moving Eurasian Plate.The result obviously indicates that the South Kunlun Fault,Central Kunlun Fault and Jinshajiang Fault are all southward thrusting.It is then presumed that the upper-mantle beneath the Qaidam Basin is rigid,where there is no exchange of hot material.
The INDEPTH-IV seismic profile,located in northeastern Qinghai-Tibetan Plateau,starts at the north end of Qaidam Basin,extends across East Kunlun Fault Zone,Jinsha Suture,and ends at Qiangtang Terrain.The authors implemented a 3-D travel-time residual reversion using body-wave from the natural earthquake,and outlined the pattern of the deep-seated structure underneath the northeast part of the Qinghai-Tibetan Plateau.The most notable phenomenon in the area of interest is the existence of low-velocity bodies distributed between the lower-crust and the upper-mantle beneath the Kunlun Terrain,Hoh Xil Terrain and the north part of Qiangtang Terrain,probably related to the hot mantle material derived from the collision between the northward thrusting Indian Plate and southward moving Eurasian Plate.The result obviously indicates that the South Kunlun Fault,Central Kunlun Fault and Jinshajiang Fault are all southward thrusting.It is then presumed that the upper-mantle beneath the Qaidam Basin is rigid,where there is no exchange of hot material.
引文
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GAO Rui,MENG Ling-shun,LI Li.1989.The Imagery Processing of Gravity Anomaly in the Yadong-Golmud Strip on Qing-hai-Xizang Plateau and its Regent Crustal Structure[J].Acta Geosicientia Sinica,11(2):162-173(in Chinese with English abstract).
GAO Rui,XIONG Xiao-song,LI Qiu-sheng,LU Zhan-wu.2009.The Moho Depth of Qinghai-Tibet Plateau Revealed by Seis-mic Detection[J].Acta Geoscientica Sinica,30(6):761-773(in Chinese with English abstract).
VERGNE J,WITTLINGER G,HUI Q TAPPONNIER P,POUPINET G,MEI J,HERQUEL G,PAUL A.2002.Seismic evidence for stepwise thickening of the crust across the NE Tibetan plateau[J].Earth Planet.Sci.Lett.,203(1):25-33.
WITTLINGER G,MESSON F,POUPINET G.1996.Seismic to-mography of northern Tibet and Kynlun:Evidence for crustal block and mantle velocity contrasts[J].Earth Planet.Sci.Lett.,139:263-279.
WITTLINGER G,TAPPONNIER P,POUPINET G.1998.Tomo-graphic Evidence for Localized Lithospheric Shear Along the Altyn Tagh Fault[J].Science,282:74-76.
WITTLINGER G,FARRA V,VERGNE J.2004.Lithospheric and upper mantle stratifications beneath Tibet:New insights from Sp conversions[J].Geophysical Research Letters,31(19):1-4.
WU Zhen-han,YE Pei-sheng,ZHAO Wen-jin,PARTRICK J B,HU Dao-gong.2007.Late Cenozoic overthrust system in the southern East Kunlun Mountains,China[J].Geological Bulle-tin of China,26(4):448-456(in Chinese with English abstract).
YIN An,DANG Yu-qi,CHEN Xuan-hua,WANG Li-qun,JIANG Wu-ming,JIANG Rong-bao,WANG Xiao-feng,ZHOU Su-ping,LIU Ming-de,MA Li-xie.2007.Cenozoic Evolution and Tectonic Reconstruction of the Qaidam Basin:Evidence From Seismic Profiles[J].Journal of Geomechanics,13(3):193-211(in Chinese with English abstract).
董树文,许志琴,吴珍汉.2009.中国地质科学院对5.12汶川地震的快速反应与调查研究[J].地球学报,30(1):21-26.
高锐,孟令顺,李莉.1989.青藏高原亚东—格尔木条带布格重力异常数字图象处理与地壳现代构造[J].地球学报,11(2):162-173.
高锐,熊小松,李秋生,卢占武.2009.由地震探测揭示的青藏高原莫霍面深度[J].地球学报,30(6):761-773.
吴珍汉,叶培盛,赵文津,PARTRICK J B,胡道功.2007.东昆仑南部晚新生代逆冲推覆构造系统[J].地质通报,26(4):448-456.
尹安,党玉琪,陈宣华,汪立群,蒋武明,蒋荣宝,王小凤,周苏平,刘明德,马立协.2007.柴达木盆地新生代演化及其构造重建——基于地震剖面的解释[J].地质力学学报,13(3):193-211.
CAI Hou-wei.2009.Present Crustal Activity Tibetan Plateau[J].Northwestern Geology,42(1):34-42(in Chinese with English abstract).
DONG Shu-wen,XU Zhi-qin,WU Zhen-han.2009.CAGS Quick Response to and Geoscientific Survey on May12Wenchuan Earthquake[J].Acta Geoscientica Sinica,30(1):21-26(in Chi-nese with English abstract).
GALVE A,HIRN A,JIANG M,GALLART J,VOOGD B D,LEPINE J C,DIAZ J,WANG Y X,QIAN H.2002.Mode of raising northeastern Tibet probed by explosion seismology[J].Earth Planet.Sci.Lett.,203(1):35-43.
GAO Rui,MENG Ling-shun,LI Li.1989.The Imagery Processing of Gravity Anomaly in the Yadong-Golmud Strip on Qing-hai-Xizang Plateau and its Regent Crustal Structure[J].Acta Geosicientia Sinica,11(2):162-173(in Chinese with English abstract).
GAO Rui,XIONG Xiao-song,LI Qiu-sheng,LU Zhan-wu.2009.The Moho Depth of Qinghai-Tibet Plateau Revealed by Seis-mic Detection[J].Acta Geoscientica Sinica,30(6):761-773(in Chinese with English abstract).
VERGNE J,WITTLINGER G,HUI Q TAPPONNIER P,POUPINET G,MEI J,HERQUEL G,PAUL A.2002.Seismic evidence for stepwise thickening of the crust across the NE Tibetan plateau[J].Earth Planet.Sci.Lett.,203(1):25-33.
WITTLINGER G,MESSON F,POUPINET G.1996.Seismic to-mography of northern Tibet and Kynlun:Evidence for crustal block and mantle velocity contrasts[J].Earth Planet.Sci.Lett.,139:263-279.
WITTLINGER G,TAPPONNIER P,POUPINET G.1998.Tomo-graphic Evidence for Localized Lithospheric Shear Along the Altyn Tagh Fault[J].Science,282:74-76.
WITTLINGER G,FARRA V,VERGNE J.2004.Lithospheric and upper mantle stratifications beneath Tibet:New insights from Sp conversions[J].Geophysical Research Letters,31(19):1-4.
WU Zhen-han,YE Pei-sheng,ZHAO Wen-jin,PARTRICK J B,HU Dao-gong.2007.Late Cenozoic overthrust system in the southern East Kunlun Mountains,China[J].Geological Bulle-tin of China,26(4):448-456(in Chinese with English abstract).
YIN An,DANG Yu-qi,CHEN Xuan-hua,WANG Li-qun,JIANG Wu-ming,JIANG Rong-bao,WANG Xiao-feng,ZHOU Su-ping,LIU Ming-de,MA Li-xie.2007.Cenozoic Evolution and Tectonic Reconstruction of the Qaidam Basin:Evidence From Seismic Profiles[J].Journal of Geomechanics,13(3):193-211(in Chinese with English abstract).
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