【摘要】 利用2009—2011年汶川震区GPS水平速度场数据,综合考虑汶川震后的余滑模型、黏弹性松弛模型及用于描述地壳长期运动的弹性块体模型,采用格网搜索法反演了汶川震区中下地壳的有效黏滞系数.地壳介质黏滞系数不同是造成震后断层两侧地壳水平运动差异的主要因素.研究发现,龙门山断裂带两侧中下地壳介质的黏滞系数差别很大.龙门山断裂以西川西块体中下地壳(16—40km)的有效黏滞系数约为7×1019Pa·s,而龙门山断裂以西、岷江断裂以东的岷江地块中下地壳(16—40km)的有效黏滞系数约为1020Pa·s,比川西地块大.龙门山断裂以东的四川盆地中下地壳(16—40km)的有效黏滞系数约为7×1022Pa·s,比岷江地块和川西地块均大,呈现极强的刚性运动特点.此外,由于同震破裂滑脱面的存在,震中附近的余滑效应比较显著.更多还原

【Abstract】 Combing with the after-slip model,the viscoelastic relaxation model and the elastic block model,this paper estimates the effective viscosity of middle to lower crust by fitting the observed GPS velocity in Wenchuan region in the period of 2009—2011.The results indicate that the effective viscosity of middle to lower crust in Wenchuan region varies largely for the two sides of Longmenshan fault zone,which impacts the kinematics’ patterns of the crust in the study region.The effective viscosity of lower crust is about 7×1019 Pa·s to the western side of Longmenshan fault except the Minjiang block which contains a slightly stronger middle to lower crust;the effective viscosity is about 7×1022 Pa·s to the eastern side of Longmenshan fault,showing a strong rigidmotion characteristics.In addition,the after-slip effect is notable because of the existing coseismic rupture surface.更多还原