位移格林函数的精密计算及其在芦山Ms7.0地震中的应用

High Accurate Computation of Green Functions for Coseismic Displacements and Its Application to the Lushan Ms7.0 Earthquake

依据目标地震震中周围地区地壳上地幔实际构造,重建层状地球模型,并据此改造格林函数计算程序,计算适用于目标地震的格林函数,从而提高同震位移计算精度。芦山Ms7.0地震震例研究表明,地球模型对垂向位移格林函数的影响随着震中距的变化而变化。4类独立震源中,地球模型对水平面内引张位错的影响最大,其在近区的影响可达到格林函数本身的40%左右。按照川西地区地壳上地幔实际层状构造（简称＂芦山模型＂）改造格林函数计算程序后,近场同震水平位移的计算精度总体上可提高20～30%。

In this paper we introduce a method that rebuilds a layered earth model according to the real structures of the crustal and upper mantle around the epicenter.Further,we modify the computing codes for displacement Green functions（DGFs）based on the above newly-built layered earth model.The new codes can calculate more suitable DGFs for the objective earthquake,therefore providing us with higher-accuracy coseismic displacements.The case study of the Lushan Ms7.0 earthquake shows that the effects of earth model on vertical DGFs change with the variation of epicentral distance.Among the four independent dislocations,the effects of the earth model on the opening tensile at a horizontal plane are biggest,up to 40% of the DGF themselves in the near field.After modifying the computing codes for DGFs according to the real structure in west Sichuan（call it＂Lushan model＂in this paper）,we improve the accuracy of coseismic displacements in the near field by 20%-30% in total.