Three‐dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton
Three‐dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton
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DOI：
10.1002/2017jb014203
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发表时间：
2017-08
期刊：
影响因子：
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通讯作者：
Xingchen Wang;Yonghua Li;Z. Ding;Lupei Zhu;Chun-yong Wang;X. Bao;Yan Wu
中科院分区：
文献类型：
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作者：
Xingchen Wang;Yonghua Li;Z. Ding;Lupei Zhu;Chun-yong Wang;X. Bao;Yan Wu
本文提出了一个新的青藏高原东北部和华北西部岩石圈三维Vs模型。首先，使用邻域算法反演高频接收器函数（RF），以估计每个台站下方的沉积结构。然后通过联合反演RF和Rayleigh波频散，构建了具有前所未有分辨率的3D Vs模型。银川-河套地堑、鄂尔多斯地块和阿拉善地块西部存在厚度2 ~ 10 km的低速沉积层。从中下地壳到上地幔的速度在鄂尔多斯地块普遍较高，而在阿拉善地块较低，表明阿拉善地块不是NCC的一部分。鄂尔多斯地块西南部和阿拉善地块西部地壳增厚，表明它们曾被改造。在昆仑断裂带和西祁连地体下发现了两个地壳低速带。KF带下方低纬带的成因可能是剪切加热、局部软流圈上涌和地壳放射性的综合作用。QLT西部的LVZ代表KF带中LVZ的早期阶段，作为滑脱作用，分离了上地壳和下地壳之间的变形，并在地震发生中起着关键作用。我们认为NETP下的地壳变形是由剪切运动、中上地壳增厚和下地壳移动的组合所适应的。
We present a new 3‐D lithospheric Vs model for the NE Tibetan Plateau (NETP) and the western North China Craton (NCC). First, high‐frequency receiver functions (RFs) were inverted using the neighborhood algorithm to estimate the sedimentary structure beneath each station. Then a 3D Vs model with unprecedented resolution was constructed by jointly inverting RFs and Rayleigh wave dispersions. A low‐velocity sedimentary layer with thicknesses varying from 2 to 10 km is present in the Yinchuan‐Hetao graben, Ordos block, and western Alxa block. Velocities from the middle‐lower crust to the uppermost mantle are generally high in the Ordos block and low in the Alxa block, indicating that the Alxa block is not part of the NCC. The thickened crust in southwestern Ordos block and western Alxa block suggests that they have been modified. Two crustal low‐velocity zones (LVZs) were detected beneath the Kunlun Fault (KF) zone and western Qilian Terrane (QLT). The origin of the LVZ beneath the KF zone may be the combined effect of shear heating, localized asthenosphere upwelling, and crustal radioactivity. The LVZ in the western QLT, representing an early stage of the LVZ that has developed in the KF zone, acts as a decollement to decouple the deformation between the upper and lower crust and plays a key role in seismogenesis. We propose that the crustal deformation beneath the NETP is accommodated by a combination of shear motion, thickening of the upper‐middle crust, and removal of lower crust.