川西藏东地区的地壳均衡异常及其与地震分布的关系
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摘要
川西藏东地区是青藏高原物质东移、转而向东南运移的通道地域,该处强烈的构造活动和频发的地震即是由于其深部物质的分异、调整和运移所致.为此,在该地域沿30°N设置了一条跨越特提斯构造域和扬子克拉通不同构造单元的剖面,依据Airy重力均衡理论求取该剖面沿线的理论均衡地壳厚度,并与根据天然地震和人工源地震资料所求得的实际地壳厚度进行对比分析,以探讨该区壳、幔物质的地壳均衡状态.研究结果发现,在本剖面沿线呈现出两处大的均衡异常区,即与四川盆地相比其差异显著,均衡异常强度高、且范围广.在此基础上通过对地壳重力场均衡效应与强烈地震活动之间关系的分析与探讨.认为存在均衡异常的地区是强震发生的主要地带,而由均衡区向不均衡区过度的均衡异常梯度带则是强震预防的重中之重.
The area of west Sichuan and east Tibet is the channel where the deep materials of the Tibetan plateau flow eastward and turn to southeast. Due to the strong differentiation, adjustment and movement of the deep materials in this area, strong tectonic activities and earthquakes occur frequently here. Hence, a profile across the Tethyan tectonic domain and the Yangzi craton has been set along the 30°N latitude. And the theoretical isostatic crustal thickness has been calculated according to the Airy isostatic theory and compared with the crustal thickness obtained from both the active and passive seismic sounding data, so as to discuss the isostatic state of the area. The result reveals that there exist two non-isostatic regions along this profile, that is to say, compared with the stable Sichuan basin, the crusts of these two regions are in quite a non-isostatic state. Based on this result, we have analyzed and discussed the relationship between isostatic anomaly and the distribution of strong earthquakes. Our result suggests that the non-isostatic area is the main zone where strong earthquakes occur frequently, and the steep gradient belt of the non-isostatic zone is the place worth more attention concerning earthquake prediction.
The area of west Sichuan and east Tibet is the channel where the deep materials of the Tibetan plateau flow eastward and turn to southeast. Due to the strong differentiation, adjustment and movement of the deep materials in this area, strong tectonic activities and earthquakes occur frequently here. Hence, a profile across the Tethyan tectonic domain and the Yangzi craton has been set along the 30°N latitude. And the theoretical isostatic crustal thickness has been calculated according to the Airy isostatic theory and compared with the crustal thickness obtained from both the active and passive seismic sounding data, so as to discuss the isostatic state of the area. The result reveals that there exist two non-isostatic regions along this profile, that is to say, compared with the stable Sichuan basin, the crusts of these two regions are in quite a non-isostatic state. Based on this result, we have analyzed and discussed the relationship between isostatic anomaly and the distribution of strong earthquakes. Our result suggests that the non-isostatic area is the main zone where strong earthquakes occur frequently, and the steep gradient belt of the non-isostatic zone is the place worth more attention concerning earthquake prediction.
引文
[1] 滕吉文,熊绍柏,张中杰.青藏高原深部结构与构造地球物理研究的回顾和展望.地球物理学报,1997,40(增刊):121～139 Teng J W,Xiong S B,Zhang Z J.Review and prospects for geophysical study of the deep lithosphere structure and tectonics in Qinghai-Xizang(Tibet)plateau.Chinese J.Geophys.(in Chinese),1997,40(Suppl.):121～139
[2] 曾融生,朱介寿,周兵等.青藏高原及东部邻区的三维地震波速度结构与大陆碰撞模型.地震学报,1992,14(增刊):523～ 533 Zeng R S,Zhu J S,Zhou B,et al.The 3D P wave velocity structure beneath the Tibetan plateau and its adjusent area and the modle of continental collision.Acta Seisrnologica Sinica(in Chinese),1994,14(Suppl.):523～533
[3] 滕吉文,张中杰,杨顶辉等.青藏高原整体隆升与地壳缩短增厚的物理-力学机制研究(上).高校地质学报,1996,2(2) :212～232 Teng J W,Zhang Z J,Yang D H,et al.Physical-mechanical mechanism for the whole uplifting of the Qinghai-Xizang plateau and the lateral shortening and vertical thickening of the crust(1st).Geological Journal of Universities(in Chinese),1996,2(2) :212～232
[4] 滕吉文,张中杰,杨顶辉等.青藏高原整体隆升与地壳缩短增厚的物理-力学机制研究(下).高校地质学报,1996,2(3) :307～323 Teng J W,Zhang Z J,Yang D H,et al.Physical-mechanical mechanism for the whole uplifting of the Qinghai-Xizang plateau and the lateral shortening and vertical thickening of the crust(2nd).Geological Journal of Universities(in Chinese),1996,2(3) :307～323
[5] Royden L H,Burchfiel B C,King R W,et al.Surface deformation and lower crustal flow in eastern Tibet.Science,1997,276(5313) :788～790
[6] 张中杰,滕吉文,李英康等.藏南地壳速度结构与地壳物质东西向“逃逸”--以佩枯错-普莫雍错宽角反射剖面为例.中国科学(D辑),2002,32(10) :793～798 Zhang Z J,Teng J W,Li Y K,et al.The velocity structure beneath the southern Tibet and the eastward“escape”of the crustal material--taking the wide-angle reflection profile from Peikucuo to Pumoyongcuo.Science in China(Series D),2002,32(10) :793～798
[7] 王椿镛,吴建平,楼海等.青藏高原东缘的地壳P波速度结构.中国科学(D辑),2002,33(增刊):181～189 Wang C Y,Wu J P,Lou H,et al.The P wave velocity structure of crust beneath the east margin of the QinghaiTibetan plateau.Science in China(Series D),2002,33(Suppl.):181～189
[8] 王椿镛,楼海,吕志勇等.青藏高原东部地壳上地幔S波速度结构--下地壳流的深部环境.中国科学(D辑),2008,38(1) :22～32 Wang C Y,Lou H,Lu Z Y,et al.The S wave velocity structure of the crust and upper mantle beneath the east margin of the Qinghai-Tibetan plateau--the deep environment for the lower crustal flow.Science in China(Series D),2008,38(1) :22～32
[9] Wang C Y,Han W B,Wu J P,et al.Crustal structure beneath the eastern margin of the Tibetan plateau and its tectonic implications.J Geophys Res,2007,112:B07307,doi:10． 1029/2005JB0000445
[10] 王谦身,张赤军,安玉林等.重力学.北京:地震出版社,2003 Wang Q S,Zhang C J,An Y L,et al.Gravity(in Chinese).Beijing.Seismological Press,2003
[11] 刘元龙,王谦身,武传真.喜马拉雅山脉中部地区的地壳构造及其地质意义探讨.地球物理学报,1977,20(2) :143～149 Liu Y L,Wang Q S,Wu C Z.A preliminary study of the crustal structure and the geological significance of the central portion of the Himalayan mountain region.Chinese J.Geophys.(in Chinese),1977,20(2) :143～149
[12] Yong Hong Shin,Xu Houze,Braitenberg,et al.Moho undulations beneath Tibet from GRACE-integrated gravity data.Geophys.J.Int.,2007,170:971～985
[13] Braitenberg C,Wang Y,Fang J,et al.Spatial variations of flexure parameters over the Tibet-Qinghai plateau.Earth and Planetary Science Letters,2003,205:211～224
[14] Yu Jin,Marcia K mcNutt,Yongsheng Zhu.Evidence from gravity and topography data for folding of Tibet.Nature,1994,371:669～674
[15] Braitenberg C,Zadro M,Fang J,et al.The gravity and isostatic Moho undulations in Qinghai-Tibet plateau.Journal of Geodynarnics,2000,30:489～505
[16] 李勇,徐公达,周荣军等.龙门山重力异常及其对青藏高原东缘山脉地壳隆升的约束.地质通报,2005,24(12) :1162～1168 Li Y,Xu G D,Zhou R J,et al.Isostatic gravity anomalies in the Longmen Mountains and their constraints on the crustal uplift below the mountains on the eastern margin of the Qinghai-Tibet Plateau.Geological Bulletin of China,2005,24(12) :1162～1168
[17] 王谦身,滕吉文,张永谦等.四川中西部地区地壳结构与重力均衡.地球物理学报,2009,52(2) :579～583 Wang Q S,Teng J W,Zhang Y Q,et al.The crustal structure and gravity isostasy in the middle western Sichuan area.Chinese J.C-eophys.(in Chinese),2009,52(2) :579～583
[18] 王谦身,滕吉文,张永谦等.龙门山断裂系及邻区地壳重力均衡效应与汶川地震.地球物理学进展,2008,23(6) :1664～1670 Wang Q S,Teng J W,Zhang Y Q,et al.The effect of crustal gravity isostasy and Wenchuan earthquake in Longmenshan faults and adjacent area.Progress in Geophys(in Chinese),2008,23(6) :1664～1670
[2] 曾融生,朱介寿,周兵等.青藏高原及东部邻区的三维地震波速度结构与大陆碰撞模型.地震学报,1992,14(增刊):523～ 533 Zeng R S,Zhu J S,Zhou B,et al.The 3D P wave velocity structure beneath the Tibetan plateau and its adjusent area and the modle of continental collision.Acta Seisrnologica Sinica(in Chinese),1994,14(Suppl.):523～533
[3] 滕吉文,张中杰,杨顶辉等.青藏高原整体隆升与地壳缩短增厚的物理-力学机制研究(上).高校地质学报,1996,2(2) :212～232 Teng J W,Zhang Z J,Yang D H,et al.Physical-mechanical mechanism for the whole uplifting of the Qinghai-Xizang plateau and the lateral shortening and vertical thickening of the crust(1st).Geological Journal of Universities(in Chinese),1996,2(2) :212～232
[4] 滕吉文,张中杰,杨顶辉等.青藏高原整体隆升与地壳缩短增厚的物理-力学机制研究(下).高校地质学报,1996,2(3) :307～323 Teng J W,Zhang Z J,Yang D H,et al.Physical-mechanical mechanism for the whole uplifting of the Qinghai-Xizang plateau and the lateral shortening and vertical thickening of the crust(2nd).Geological Journal of Universities(in Chinese),1996,2(3) :307～323
[5] Royden L H,Burchfiel B C,King R W,et al.Surface deformation and lower crustal flow in eastern Tibet.Science,1997,276(5313) :788～790
[6] 张中杰,滕吉文,李英康等.藏南地壳速度结构与地壳物质东西向“逃逸”--以佩枯错-普莫雍错宽角反射剖面为例.中国科学(D辑),2002,32(10) :793～798 Zhang Z J,Teng J W,Li Y K,et al.The velocity structure beneath the southern Tibet and the eastward“escape”of the crustal material--taking the wide-angle reflection profile from Peikucuo to Pumoyongcuo.Science in China(Series D),2002,32(10) :793～798
[7] 王椿镛,吴建平,楼海等.青藏高原东缘的地壳P波速度结构.中国科学(D辑),2002,33(增刊):181～189 Wang C Y,Wu J P,Lou H,et al.The P wave velocity structure of crust beneath the east margin of the QinghaiTibetan plateau.Science in China(Series D),2002,33(Suppl.):181～189
[8] 王椿镛,楼海,吕志勇等.青藏高原东部地壳上地幔S波速度结构--下地壳流的深部环境.中国科学(D辑),2008,38(1) :22～32 Wang C Y,Lou H,Lu Z Y,et al.The S wave velocity structure of the crust and upper mantle beneath the east margin of the Qinghai-Tibetan plateau--the deep environment for the lower crustal flow.Science in China(Series D),2008,38(1) :22～32
[9] Wang C Y,Han W B,Wu J P,et al.Crustal structure beneath the eastern margin of the Tibetan plateau and its tectonic implications.J Geophys Res,2007,112:B07307,doi:10． 1029/2005JB0000445
[10] 王谦身,张赤军,安玉林等.重力学.北京:地震出版社,2003 Wang Q S,Zhang C J,An Y L,et al.Gravity(in Chinese).Beijing.Seismological Press,2003
[11] 刘元龙,王谦身,武传真.喜马拉雅山脉中部地区的地壳构造及其地质意义探讨.地球物理学报,1977,20(2) :143～149 Liu Y L,Wang Q S,Wu C Z.A preliminary study of the crustal structure and the geological significance of the central portion of the Himalayan mountain region.Chinese J.Geophys.(in Chinese),1977,20(2) :143～149
[12] Yong Hong Shin,Xu Houze,Braitenberg,et al.Moho undulations beneath Tibet from GRACE-integrated gravity data.Geophys.J.Int.,2007,170:971～985
[13] Braitenberg C,Wang Y,Fang J,et al.Spatial variations of flexure parameters over the Tibet-Qinghai plateau.Earth and Planetary Science Letters,2003,205:211～224
[14] Yu Jin,Marcia K mcNutt,Yongsheng Zhu.Evidence from gravity and topography data for folding of Tibet.Nature,1994,371:669～674
[15] Braitenberg C,Zadro M,Fang J,et al.The gravity and isostatic Moho undulations in Qinghai-Tibet plateau.Journal of Geodynarnics,2000,30:489～505
[16] 李勇,徐公达,周荣军等.龙门山重力异常及其对青藏高原东缘山脉地壳隆升的约束.地质通报,2005,24(12) :1162～1168 Li Y,Xu G D,Zhou R J,et al.Isostatic gravity anomalies in the Longmen Mountains and their constraints on the crustal uplift below the mountains on the eastern margin of the Qinghai-Tibet Plateau.Geological Bulletin of China,2005,24(12) :1162～1168
[17] 王谦身,滕吉文,张永谦等.四川中西部地区地壳结构与重力均衡.地球物理学报,2009,52(2) :579～583 Wang Q S,Teng J W,Zhang Y Q,et al.The crustal structure and gravity isostasy in the middle western Sichuan area.Chinese J.C-eophys.(in Chinese),2009,52(2) :579～583
[18] 王谦身,滕吉文,张永谦等.龙门山断裂系及邻区地壳重力均衡效应与汶川地震.地球物理学进展,2008,23(6) :1664～1670 Wang Q S,Teng J W,Zhang Y Q,et al.The effect of crustal gravity isostasy and Wenchuan earthquake in Longmenshan faults and adjacent area.Progress in Geophys(in Chinese),2008,23(6) :1664～1670
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