汶川地震震后余滑和震后粘弹性松弛数值模拟分析

采用2010~2015年汶川地区GNSS震后形变资料，利用有限元法建立三维震后粘弹性松弛模型，通过二维格网搜索获得龙门山断裂带上盘最佳弹性层厚度和中下地壳最佳粘滞系数，并分析汶川地震震后2~7 a粘弹性松弛影响下的震后形变特征；然后采用2008~2009年GNSS震后形变资料，根据最佳参数建立粘弹性松弛与余滑组合模型，并与单一余滑模型进行对比，分析汶川地震震后1 a内的形变特征。研究结果表明，根据模拟值计算得到青藏高原东部弹性层的最佳厚度为25 km，中下地壳的最佳粘滞系数为4.0×10¹⁸ Pa·s；震后1 a内组合模型的拟合效果优于单一余滑模型，其中余滑形变占主要成分。

Numerical Simulation Analysis of After-Slip and Viscoelastic Relaxation after the Wenchuan Earthquake

We use the GNSS post-seismic deformation data in the Wenchuan area from 2010 to 2015, and establish a three-dimensional post-seismic viscoelastic relaxation model using the finite element method. The two-dimensional grid search is used to obtain the optimal thickness of the elastic layer and the best viscosity coefficient of the middle and lower crust. We analyze the post-seismic deformation characteristics under the influence of viscoelastic relaxation 2-7 years after the Wenchuan earthquake. The GNSS post-seismic deformation data during 2008-2009 are used as constraints to obtain the best parameters. We compare the combined model of elastic relaxation and afterslip with the afterslip model to analyze the deformation characteristics within one year of the Wenchuan earthquake. The results show that the optimal thickness of the elastic layer in the eastern part of the Tibet plateau is 25 km, the optimal viscosity coefficient of the middle and lower crust is 4.0×10¹⁸ Pa·s. The fitting effect of the combined model is better than that of the single afterslip model within one year after the earthquake, and the afterslip deformation is the main component.