Seismic signature of the collision between the east Tibetan escape flow and the Sichuan Basin
Seismic signature of the collision between the east Tibetan escape flow and the Sichuan Basin
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藏东逃逸流与四川盆地碰撞的地震特征
DOI：
10.1016/j.epsl.2010.01.046
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发表时间：
2010-04
影响因子：
5.3
通讯作者：
Teng, Jiwen
中科院分区：
文献类型：
--
作者：
Zhang, Zhongjie;Yuan, Xiaohui;Chen, Yun;Tian, Xiaobo;Kind, Rainer;Li, Xueqing;Teng, Jiwen
GPS位移矢量显示，由于印度板块的北向运动，藏东地壳正受到挤压，四川盆地正在抵抗这股水流，并将其主要转向印度支那。龙门山是西藏最陡峭的高原隆起，是藏东逸流与刚性扬子地块(四川盆地)强烈相互作用的结果，但这种相互作用的运动学和动力学仍是一些争论的主题。本文介绍了从四川盆地到西藏东部的一条致密的无源地震剖面的结果，以研究该碰撞带的深部结构。利用P和S接收函数图像，在四川盆地下方120~150公里和藏东地区下方70~80公里处，观测到岩石圈-软流圈边界(LAB)的突然上升。相反，壳幔边界(MOHO)深度在四川盆地以下从36公里增加到40公里，在西藏东部从55公里增加到60公里。这条410公里长的断裂面位于西藏东部以下约30公里处，尽管整个LMS的660公里断裂面几乎保持在相同的深度。根据这些观察，我们得出结论，西藏与四川盆地之间发生的碰撞模式与印度与西藏之间的碰撞模式非常不同。在藏南，我们实质上观察到了印度板块的俯冲，印度板块向北穿透到西藏中部下方数百公里处。藏东岩石圈极薄的地幔部分可能指示了岩石圈底部的拆沉或被热的软流圈逸出流带走。这一过程导致了西藏东部边缘异常陡峭的地形，这是重力浮力的结果。这一观点得到了西藏东部410公里不连续面异常下沉的支持，这可能是次垂直向下软流圈流动的动力学所致。
GPS displacement vectors show that the crust in east Tibet is being squeezed in an easterly direction by the northward motion of the Indian plate, and the Sichuan Basin is resisting this stream and redirecting it mainly towards Indochina. The Longmen Shan, containing the steepest rise to the high plateau anywhere in Tibet, results from the strong interaction between the east Tibetan escape flow and the rigid Yangtze block (Sichuan Basin), but the kinematics and dynamics of this interaction are still the subject of some debates. We herein present results from a dense passive-source seismic profile from the Sichuan Basin into eastern Tibet in order to study the deep structure of this collision zone. Using P and S receiver function images we observe a sudden rise of the Lithosphere–Asthenosphere Boundary (LAB) from 120 to 150km beneath the Sichuan Basin and from 70 to 80km beneath eastern Tibet. In contrast, the depth of the crust–mantle boundary (Moho) increases from 36 to 40km beneath the Sichuan Basin and from 55 to 60km beneath eastern Tibet. The 410km discontinuity is depressed below eastern Tibet by about 30km, although the 660 remains at nearly the same depth throughout the LMS. From these observations, we conclude that the mode of collision that occurs between Tibet and the Sichuan Basin is very different to that found between India and Tibet. In southern Tibet, we observe in essence the subduction of the Indian plate, which penetrates northwards for several hundred kilometers under central Tibet. The very thin mantle part of the lithosphere beneath eastern Tibet may indicate delamination or removal of the bottom of the lithosphere by hot asthenospheric escape flow. This process leads to the exceptionally steep topography at the eastern Tibetan margin as a result of gravitational buoyancy. This view is supported by the very unusual depression of the 410km discontinuity beneath eastern Tibet, which could be caused by the dynamics of the sub-vertical downward asthenospheric flow.
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影响因子：
--
作者：
X. Yuan;J. Ni;R. Kind;J. Mechie;E. Sandvol
通讯作者：
X. Yuan;J. Ni;R. Kind;J. Mechie;E. Sandvol
DOI：
10.1002/cjg2.1218
发表时间：
2008-03
期刊：
Chinese Journal of Geophysics
影响因子：
--
作者：
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通讯作者：
G. Yi;H. Yao;Jie-shou Zhu;R. Hilst
影响因子：
5.3
作者：
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通讯作者：
X. Li;S. Sobolev;R. Kind;X. Yuan;C. Estabrook
影响因子：
5.2
作者：
H. Yusa;T. Inoue
通讯作者：
H. Yusa;T. Inoue
影响因子：
2.8
作者：
KENNETT, BLN;ENGDAHL, ER
通讯作者：
ENGDAHL, ER