Receiver function structures beneath the deep large faults in the northeastern margin of the Tibetan Plateau
Receiver function structures beneath the deep large faults in the northeastern margin of the Tibetan Plateau
复制标题
青藏高原东北缘深大断裂下方的接收函数结构
DOI：
10.1016/j.tecto.2013.10.011
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发表时间：
2014-01
期刊：
影响因子：
2.9
通讯作者：
Li, Cuiqin
中科院分区：
文献类型：
--
作者：
Liu, Xuzhou;Qin, Manzhong;Wei, Congxin;Li, Cuiqin
利用高密度线性临时地震台阵的纵横波接收功能，对青藏高原东北缘深大断裂下的地壳和上地幔结构进行了成像。第一转换波和多次波图像表明，西秦岭北断裂带和迭部-略阳断裂切割了莫霍面，使断裂两侧莫霍面具有明显的差异特征。高Vp/Vs值和低速层出现在靠近青藏高原的台阵西部，这意味着来自青藏高原的下地壳通道流。在鄂尔多斯附近的阵列的东部部分下方的弱莫霍面和较高的Vp/Vs比表明热地幔物质的上涌。结果还表明，在上地壳中存在明显的变形，在阵列中部以下的Vp/Vs比值较低。这种上地壳变形与地表地形密切相关，因此，我们推断青藏高原隆升过程中，脆性上地壳变形伴随着局部地形的形成，这也是研究区地震活动活跃的主要原因。岩石圈-软流圈边界（LAB）的变形还可能与印度板块俯冲引起的逆冲板块上涌，上地幔热物质上涌形成底辟有关。下地壳通道流、地壳缩短和地幔底辟作用在局部地区同时存在，表明青藏高原的隆升和形成不能用单一的模式来解释。高分辨率的地壳和地幔，特别是块体边界以下的结果，是必要的，以建立完整的地球动力学模型，以了解青藏高原的形成。
Using the teleseismic P- and S-wave receiver functions of the dense linear temporary seismic array, the crust and uppermost mantle structures beneath the deep large faults in the northeastern margin of the Tibetan Plateau were imaged. The images of the first converted wave and the multiples indicated that the North Fault Zone of West Qinling (NWQ) Mountain and Diebu–Lueyang (DBL) faults cut the Mohorovicic (Moho) Discontinuity and cause an obvious difference feature for the Moho in the two sides of the faults. The higherVp/Vsratio and lower velocity layer is found beneath the west portion of the array near the Tibetan Plateau, which implies a lower crust channel flow coming from the Tibetan Plateau. The weak Moho and higherVp/Vsratio beneath the eastern portion of the array near the Ordos suggest the upwelling of the hot mantle material. The results also indicate an obvious deformation in the upper crust with the lowerVp/Vsratio beneath the middle of the array. Such upper crust deformation is closely related to the topography of the surface; therefore, we deduce that the deformation of the brittle upper crust is accompanied by the formation of the local topography during the uplift of the Tibetan Plateau, which is also the primary reason for the active seismicity in the study region. The deformation of the lithosphere–asthenosphere boundary (LAB) can also be associated with the formation of the diapir caused by the upwelling hot materials in the upper mantle due to the uprising of the thrusting plate caused by the subduction of the India Plate. The existence of the lower crust channel flow, the crust shortening, and the mantle diapir in the local region simultaneously implies that the elevation and formation of the Tibetan Plateau cannot be explained with a single model. The higher resolution results for the crust and the mantle, especially beneath the block boundary region, are necessary to construct the completed geodynamic model to understand the formation of the Tibetan Plateau.
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