Lithospheric SH Wave Velocity Structure Beneath the Northeastern Tibetan Plateau From Love Wave Tomography
Lithospheric SH Wave Velocity Structure Beneath the Northeastern Tibetan Plateau From Love Wave Tomography
复制标题
DOI：
10.1029/2019jb017788
复制
发表时间：
2019-09
期刊：
影响因子：
--
通讯作者：
Yuanyuan V. Fu;Lun Li;Zhuowei Xiao
中科院分区：
文献类型：
--
作者：
Yuanyuan V. Fu;Lun Li;Zhuowei Xiao
青藏高原东北部（NE）一直是了解青藏高原上升和横向生长动态过程的主要场所。本文利用 ChinArray II 和中国数字地震台阵采用双平面波方法记录的地震数据，基于基模 Love 波频散（20-100 s）的测量，构建了青藏高原东北部及其邻近地区的高分辨率岩石圈尺度各向同性 SH 波速度模型（深度至 130 km）。在青藏高原东北部的中下地壳，特别是在祁连造山带和松潘-甘孜地体地区，观察到了显着的慢SH波速（VSH），这与先前指出的显着的慢SV波速（VSV）一致，可能暗示中下地壳存在部分熔融。这种低SH波速度异常可以追溯到最上地幔，表明岩石圈较弱且温暖，我们将其解释为青藏高原东北部岩石圈地幔去除后软流圈上涌的结果。软流圈上升流和相关的深层热浮力可以解释中下地壳部分熔融的发生，并解释青藏高原东北部的部分高海拔地区。西秦岭造山带大部分岩石圈存在高速异常，这与青藏高原沿秦岭造山带岩石圈内河道流的存在不符。
The northeastern (NE) Tibetan plateau has been a prime site to understand the dynamic processes responsible for the rise and lateral growth of the Tibetan plateau. Here we construct a high‐resolution lithospheric scale isotropic SH wave velocity model (down to the depth of 130 km) for the NE Tibetan plateau and its adjacent regions based on the measurements of fundamental‐mode Love wave dispersions (20–100 s) with seismic data recorded by ChinArray II and China Digital Seismic Array using two‐plane wave method. Prominent slow SH wave velocity (VSH) is observed in the midlower crust of the NE Tibetan plateau, specifically in the Qilian Orogenic Belt and the Songpan‐Ganzi Terrane regions, coincident with previously indicated significantly slow SV wave velocity (VSV), probably implying the existence of partial melts in the midlower crust. This low SH wave velocity anomaly could be traced down to the uppermost mantle, indicating a weak and warm lithosphere, which we interpret as a consequence of asthenosphere upwelling after lithospheric mantle removal in the NE Tibetan plateau. The asthenosphere upwelling and associated deep‐seated thermal buoyancy could explain the occurrence of partial melting in the mid‐lower crust and account for parts of high elevations in the NE Tibetan plateau. The western Qinling orogenic belt is characterized with a high velocity anomaly in most of lithosphere, which is inconsistent with the existence of channel flow within the lithosphere along the Qinling orogenic belt from the Tibetan plateau.