亚洲东部“大三角”地震构造区的周边和深部动力环境
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摘要
亚洲东部存在一个巨大的三角形地震构造区域,大体上,喜马拉雅山脉、帕米尔—天山—阿尔泰山—贝加尔和东经105°线是它的3个边界,主要覆盖中国和蒙古国西部众多高原、山脉及山间盆地。三角区内现今构造活动和地震广泛强烈,地壳破碎,显示不均匀的块体边界和块内变形;区外基本上是稳定的刚性陆块,地震很少,变形较弱,处于整体缓慢运动之中。这个宽阔的板内变形区起源于印度、菲律宾海—西太平洋和欧亚三大板块之间的动力作用以及深部地幔流的影响。向北快速运动的印度次大陆已近水平地插入到西藏板块下,沿喜马拉雅弧产生多种运动和变形,并向亚洲内部远距离地扩散。沿东经95°～100°,向北的地壳运动向东和东南方向偏转,阻截了喜马拉雅弧东端的北向运动;而在喜马拉雅弧西端,帕米尔继续向北挤进中亚,受天山—阿尔泰山—贝加尔一线西北側稳定地壳的限制,扩散的变形被中国、蒙古、俄罗斯边境地区一系列EW向和NW向的老断层吸收并在它们的西端终止。菲律宾海—西太平洋向欧亚大陆的消减-俯冲导致沿海沟-岛弧的漫长而狭窄的地震带,但对亚洲大陆的水平挤压较小,未能阻挡亚洲大陆东部向东移动。其部分原因可能是俯冲板片受到来自欧亚大陆下的ES向地幔流的推挤,这个ES向地幔流与来自印度下面的N向地幔流在西藏中部汇合并向东偏转,在大尺度上与GPS观测到的地表移动图像一致。
In eastern Asia,there exists a huge triangle-shaped tectonic region with extensive major earthquakes. Roughly,the Himalayan arc,Pamirs-Altai-Baikal,and 105°E are the three boundaries of this region which covers plateaus,mountains and intermountain basins. Within this triangle region,the fragmented crust is characterized by intensive tectonic motion and extensive deformation that occurred along boundaries between blocks as well as in blocks. Outside this region,the rigid massifs moved as a whole with little quakes and weak deformation. On a large tectonic scale,such a broad intraplate deformation region was originated from dynamic interactions between the India,Philippine Sea-West Pacific and Eurasia plates,as well as the impact of mantle flow at depth. The Indian subcontinent that was moving toward north at about 40 mm/a had plunged beneath Tibet,resulting in various motions and deformation along the Himalayan arc,which diffused over a long distance in the hinterland of Asia. Along 95°-100°E the originally northward crustal motion turned to east and southeast,impeding the northward motion around the eastern Himalayan syntaxis. At the western Himalayan syntaxis,the Pamirs continued to move into central Asia leading to crustal deformation and earthquakes which were largely accommodated by those old EW or NW trending faults in the bordering areas between China,Mongolia and Russia,and restricted by the stable land northwest of Tian Shan-Altai-Baikal. The subduction of the Philippine and Pacific plates to the Eurasian continent had generated a very long and narrow seismic zone along trenches and island-arcs in the marginal seas,while posed a little horizontal compression on the Asian continent,thus unable to impede the eastward motion of eastern Asian continent. The partial reason for this is likely the impact of southeastward mantle flow beneath Eurasia on the subducting slabs; the southeastward mantle flow converged with the northward mantle flow from below India in central Tibet where they turned toward east and southeast,which is consistent with the pattern of surface movements observed by GPS.
In eastern Asia,there exists a huge triangle-shaped tectonic region with extensive major earthquakes. Roughly,the Himalayan arc,Pamirs-Altai-Baikal,and 105°E are the three boundaries of this region which covers plateaus,mountains and intermountain basins. Within this triangle region,the fragmented crust is characterized by intensive tectonic motion and extensive deformation that occurred along boundaries between blocks as well as in blocks. Outside this region,the rigid massifs moved as a whole with little quakes and weak deformation. On a large tectonic scale,such a broad intraplate deformation region was originated from dynamic interactions between the India,Philippine Sea-West Pacific and Eurasia plates,as well as the impact of mantle flow at depth. The Indian subcontinent that was moving toward north at about 40 mm/a had plunged beneath Tibet,resulting in various motions and deformation along the Himalayan arc,which diffused over a long distance in the hinterland of Asia. Along 95°-100°E the originally northward crustal motion turned to east and southeast,impeding the northward motion around the eastern Himalayan syntaxis. At the western Himalayan syntaxis,the Pamirs continued to move into central Asia leading to crustal deformation and earthquakes which were largely accommodated by those old EW or NW trending faults in the bordering areas between China,Mongolia and Russia,and restricted by the stable land northwest of Tian Shan-Altai-Baikal. The subduction of the Philippine and Pacific plates to the Eurasian continent had generated a very long and narrow seismic zone along trenches and island-arcs in the marginal seas,while posed a little horizontal compression on the Asian continent,thus unable to impede the eastward motion of eastern Asian continent. The partial reason for this is likely the impact of southeastward mantle flow beneath Eurasia on the subducting slabs; the southeastward mantle flow converged with the northward mantle flow from below India in central Tibet where they turned toward east and southeast,which is consistent with the pattern of surface movements observed by GPS.
引文
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[19]Calais E,Vergnolle M,Sankov V,et al.GPS measurements of crustal deformation in the Baikal-Mongolia area(1994-2002):I mplications for crustal kinematics of Asia[J].Jour-nal of Geophysical Research,2003,108(B10):2501.
[20]Enkin R J,Yang Z Y,Chen Y,et al.Paleomagnetic con-straints on the geodynamic history of the major blocks of Chi-na fromthe Permian to the present[J].Journal of Geophysi-cal Research,1992,97(B10):13953-13989.
[21]Romanowicz B.The thickness of tectonic plates[J].Science,2009,234:474-476.
[22]Tani moto T.Long-wavelength S-wave velocity structure throughout the mantle[J].Geophysical Journal Internation-al,1990,100:327-336.
[23]Holt WE.Correlated crust and mantle strain fields in Tibet[J].Geology,2000,28(1):67-70.
[24]Luo Z H,Mo X X,Hou Z Q,et al.Anintegrated model for the Cenozoic evolution of the Tibetan plateau:Constraints fromigneous rocks[J].Earth Science Frontiers,2006,13(4):196-211(in Chinese).
[25]Manga M.Shaken,not stirred[J].Nature,2001,410:1041-1043.
[26]Lombardi A M,Marzocchi W.Evidence of clustering and nonstationarity in the ti me distribution of large worldwide earthquakes[J].Journal of Geophysical Research,2007,112(B02):303.
[27]Chery J,Carretier S,Ritz J.Postseismic stress transfer ex-plains clustering of larger earthquakes in Mongolia[J].Earth and Planetary Science Letters,2001,194:277-286.
[28]Deng Q D.Some thoughts ontheMs8.0Wenchuan,Sichuan earthquake[J].Seismology and Geology,2008,30(4):811-827(in Chinese).
[29]Cyranoski D.Aseismic shift in thinking[J].Nature,2008,431:1032-1034.
[1]马宗晋,郑大林.中蒙大陆中轴构造带及其地震活动[J].地震研究,1981,4(4):421-436.
[18]冯锐,马宗晋,方剑,等.发展中的板块边界:天山—贝加尔活动构造带[J].地学前缘,2007,14(4):1-17.
[24]罗照华,莫宣学,侯增谦,等.青藏高原新生代形成演化的整合模型:来自火成岩的约束[J].地学前缘,2006,13(4):196-211.
[28]邓起东.关于四川汶川8.0级地震的思考[J].地震地质,2008,30(4):811-827.
[2]Vergnolle M,Calais E,Dong L.Dynamics of continental de-formation in Asia[J].Journal of Geophysical Research,2007,112(B11):403.
[3]Molnar P,Tapponnier P.Cenozoic tectonics of Asia:Effects of a continental collision[J].Science,1975,189:419-426.
[4]Banerjez P,Burgmann R,Nagarjan B,et al.Intraplate de-formation of the Indian subcontinent[J].Geophysical Re-search Letters,2008,35(L18):301.
[5]Sella G F,Dixon T H,Mao A.REVEL:A model for recent plate velocities fromspace geodesy[J].Journal of Geophysi-cal Research,2002,107(B4).doi:10.1029/2000JB00033.
[6]Til man F,Ni J,I NDEPTHIII Team.Seismici maging of the downwelling Indian lithosphere beneath central Tibet[J].Science,2003,300:1424-1427.
[7]Priestey K,Debayle E,McKenzie D,et al.Upper mantle structure of eastern Asia from multi mode surface waveform tomography[J].Journal of Geophysical Research,2006,111(B10):304.
[8]Li C,van der Hilst R D,Meltzer A S.et al.Subduction of the Indianlithosphere beneaththe Tibetan Plateau and Burma[J].Earth and Planetary Science Letters,2008,274(1/2):157-168.
[9]Dain A,Tapponnier P,Molnar P.Active faulting andtecton-ics of Burma and surrounding regions[J].Journal of Geo-physical Research,1984,89(B1):453-472.
[10]Vigny C,Socquet A,Rangin C,et al.Present-day crustal deformation around Sagaing fault,Myanmar[J].Journal of Geophysical Research,2003,108(B11):2533.
[11]Burt man VS,Molnar P.Geological and geophysical evidence for deep subduction of continental crust beneath the Pamir[J].Geological Society of America Special Paper,1993,281:1-76.
[12]Pegler G,Das S.An enhanced i mage of the Pamir-Hindu Kush seismic zone fromrelocated earthquake hypocenters[J].Geophysical Journal International,1998,134(2):573-595.
[13]Reigber C H,Michel G W,Galas R,et al.Newspace geo-detic constraints on the deformation of deformationin Central Asia[J].Earth and Planetary Science Letters,2001,191:157-165.
[14]Rau R,Ching K,Hu J,et al.Crustal deformation and block kinematics in transition from collision to subduction:Global positioning system measurements in northern Tai wan,1995-2005[J].Journal of Geophysical Research,2008,113(B09):404.
[15]Houseman G,England P.Crustal thickening versus lateral expulsionin the India-Asian continental collision[J].Journal of Geophysical Research,1993,98(B7):12233-12249.
[16]Royden L H.The tectonic expression of slab pull at continen-tal convergent boundaries[J].Tectonics,1993,12(2):303-325.
[17]Northrup CJ,Royden L H,Burchfiel B C.Motion of the Pa-cific plate relative to Eurasia and its potential relation to Ce-nozoic extension along the eastern margin of Eurasia[J].Ge-ology,1995,23(8):719-722.
[18]Feng R,Ma ZJ,Fang J,et al.Adeveloping plate boundary:Tianshan-Baykal active tectonic belt[J].Earth Science Fron-tiers,2007,14(4):1-17(in Chinese).
[19]Calais E,Vergnolle M,Sankov V,et al.GPS measurements of crustal deformation in the Baikal-Mongolia area(1994-2002):I mplications for crustal kinematics of Asia[J].Jour-nal of Geophysical Research,2003,108(B10):2501.
[20]Enkin R J,Yang Z Y,Chen Y,et al.Paleomagnetic con-straints on the geodynamic history of the major blocks of Chi-na fromthe Permian to the present[J].Journal of Geophysi-cal Research,1992,97(B10):13953-13989.
[21]Romanowicz B.The thickness of tectonic plates[J].Science,2009,234:474-476.
[22]Tani moto T.Long-wavelength S-wave velocity structure throughout the mantle[J].Geophysical Journal Internation-al,1990,100:327-336.
[23]Holt WE.Correlated crust and mantle strain fields in Tibet[J].Geology,2000,28(1):67-70.
[24]Luo Z H,Mo X X,Hou Z Q,et al.Anintegrated model for the Cenozoic evolution of the Tibetan plateau:Constraints fromigneous rocks[J].Earth Science Frontiers,2006,13(4):196-211(in Chinese).
[25]Manga M.Shaken,not stirred[J].Nature,2001,410:1041-1043.
[26]Lombardi A M,Marzocchi W.Evidence of clustering and nonstationarity in the ti me distribution of large worldwide earthquakes[J].Journal of Geophysical Research,2007,112(B02):303.
[27]Chery J,Carretier S,Ritz J.Postseismic stress transfer ex-plains clustering of larger earthquakes in Mongolia[J].Earth and Planetary Science Letters,2001,194:277-286.
[28]Deng Q D.Some thoughts ontheMs8.0Wenchuan,Sichuan earthquake[J].Seismology and Geology,2008,30(4):811-827(in Chinese).
[29]Cyranoski D.Aseismic shift in thinking[J].Nature,2008,431:1032-1034.
[1]马宗晋,郑大林.中蒙大陆中轴构造带及其地震活动[J].地震研究,1981,4(4):421-436.
[18]冯锐,马宗晋,方剑,等.发展中的板块边界:天山—贝加尔活动构造带[J].地学前缘,2007,14(4):1-17.
[24]罗照华,莫宣学,侯增谦,等.青藏高原新生代形成演化的整合模型:来自火成岩的约束[J].地学前缘,2006,13(4):196-211.
[28]邓起东.关于四川汶川8.0级地震的思考[J].地震地质,2008,30(4):811-827.
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