基于2015年尼泊尔MW7.8地震震后形变探测青藏高原南缘的岩石圈流变结构

基于有限元方法，采用2015年尼泊尔MW7.8地震震后5 a的GPS观测资料约束青藏高原南缘的岩石圈流变结构，利用通过主前缘逆冲断裂带(MFT)间的距离来约束边界位置的垂直边界结构和印度弹性俯冲板片结构探测印度板块和青藏高原板块的边界结构。结果表明，2种结构均能产生与观测数据一致的南-西南水平运动模式，并能较好地解释远场地面位移，但垂直边界结构模型得到的垂直形变偏大，而俯冲板片结构模型能很好地解释中尼边境及以北地区的隆升现象。青藏高原下地壳稳态和瞬态粘滞系数的最优结果分别为1×1018 Pa·s和1×1017 Pa·s。

Probing the Rheological Structure of Southern Tibet from the Postseismic Deformation of the 2015 Mw7.8 Nepal Earthquake

Based on the finite element method, we use the postseismic GPS observation data from 5 years of the 2015 MW7.8 Nepal earthquake to constrain the rheological structure of the southern Tibet. We use two different boundary structural models to probe the boundary structure of the Indian plate and the Tibetan plateau, which are the vertical boundary structure constrained by the distance between the main front thrust(MFT) and the Indian elastic subduction slab structure, respectively. The results show that both structures can produce south-southwest horizontal motion pattern consistent with the observed data, and can explain the far-field surface displacements well. The vertical deformation obtained by the vertical boundary structure is larger. In contrast, the subduction slab structure can well explain the uplift of the Sino-Nepal border and the north. The optimal results of steady state viscosity ηm and transient state viscosity ηk of the lower crust of the Tibetan plateau are 1×1018 Pa·s and 1×1017 Pa·s, respectively.