依据GPS结果,采用“块体加载”有限元方法对汶川地震前后山西断陷带的地壳运动进行数值模拟.结果显示:震前该区呈相对均一的NW向拉张,震后以构造挤压为主,南端为强烈拉张,主压应力最高值为前期5～6倍,主张应力最高值为前期的2倍,主压应力方向自北而南由NW向转为NEE向.这些与跨断层短水准、长剖面水准、GPS长基线时序曲线等解算结果一致,表明汶川地震后鄂尔多斯与华北平原块体之间相对挤压、扭错增强,并导致山西断陷带地壳形变与构造应力场变化明显.%Based on the newly obtained GPS data and the "block loading" FEA method,the crustal movement of Shanxi rift zone within two time span (1999-2007,2007-2009),which before and after the Wenchuan earthquake are simulated,respectively.The results show that the stress and strain fields assume opproximately unifrom NW-SE extension before the earthquake.However,after the earthquake they are featured with remarkable compression accompanied with notable extension in the south region.Compared with 1999-2007,in 2007-2009 the maximum principal compressive and tensile stress increases 5-6 times and about 2 times,respectively,and from the north region to the south region of Shanxi rift zone,the direcion of the principal compressive stress changes from NW to NEE.Such stress and strain variation is verified by time-series of across-fault short level survey,long distance level survey and baseline of GPS continuous site.It indicates that the compressive and strike-slip displacement between Erdos block and North China Plain block increased after the Wenchuan earthquake.As a result,the crustal deformation and tectonic stress field of the Shanxi rift zone,which located in the boundary of the two blocks,change distinctly.
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