P Wave Anisotropic Tomography of the SE Tibetan Plateau: Evidence for the Crustal and Upper‐Mantle Deformations
P Wave Anisotropic Tomography of the SE Tibetan Plateau: Evidence for the Crustal and Upper‐Mantle Deformations
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DOI：
10.1029/2018jb016048
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发表时间：
2018-10
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影响因子：
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通讯作者：
Zhouchuan Huang;Liangshu Wang;Mingjie Xu;Dapeng Zhao
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作者：
Zhouchuan Huang;Liangshu Wang;Mingjie Xu;Dapeng Zhao
青藏高原东南部的上地壳正围绕东喜马拉雅构造结顺时针旋转，扬子地块西缘已卷入活动构造。然而，深部地壳和上地幔是否以及如何对高原扩张作出反应，目前还不清楚。在这项研究中，我们提出了一个高分辨率的三维模型的P波速度层析成像和方位各向异性的地壳和上地幔下的青藏高原东南部使用走时数据记录的密集的地震网络。在扬子区西南缘地壳深部和上地幔的高速体周围发现了广泛的低速带，其方位各向异性的快速度方向大多平行于高原边缘的地形等高线和莫霍面深度沿着。这些结果表明，重力位在青藏高原东南部的地壳和上地幔变形中起着重要的作用。同时，浅部地壳可能下降到深部地壳，并驱动韧性深部地壳物质侵入邻近地区。被挤压的地壳被困在地壳深部的角落里，并被周围的坚固块体所阻挡。被困的地壳物质可能会上升，导致地表显著的隆起和高热流。
The upper crust in the SE Tibetan Plateau is rotating around the eastern Himalayan syntax clockwise, and the western margin of the Yangtze Craton has been involved in the active tectonics. However, it is still unclear whether and how the deep crust and upper mantle respond to the plateau expansion. In this study we present a high‐resolution three‐dimensional model of P wave velocity tomography and azimuthal anisotropy in the crust and uppermost mantle beneath the SE Tibetan Plateau determined using traveltime data recorded by a dense seismic network. Widespread low‐velocity zones are revealed around a high‐velocity body in the deep crust and uppermost mantle beneath the southwest Yangtze Craton, where fast‐velocity directions of the azimuthal anisotropy are mostly parallel to the contour lines of the surface topography and the Moho depth along the plateau margin. These results indicate that gravitational potential plays an important role in the crustal and uppermost‐mantle deformations in the SE Tibetan Plateau. Meanwhile, the shallow crust may drop down to the deep crust and drive the ductile deep‐crustal material to intrude into the adjacent regions. The extruded crust is trapped in a deep‐crustal corner and obstructed by the surrounding strong blocks. The trapped crustal material may rise up, causing significant uplift and high heat flow at the surface.