中文摘要：

推导三维形变数据的四边形法计算地壳主应变、剪应变的解析表达式,结合汶川地区2005~2008三维空间监测数据,计算该地区水平、垂直主应变和剪应变。结果表明,汶川、映秀地区的水平主应变在东西方向处于挤压状态,主断裂带东南区域的垂直主应变为正值,西北区域为负值,与研究区域东南部地表下沉、西北部地表抬升相关。主应变最大值出现在Y（东）方向,剪应变最大值出现在XY（北东）方向,汶川区域处于主应变和剪应变的高梯度带,与地震发生位置相吻合。

英文摘要：

The analytic expressions of principal strain and shear strain are deduced by quadrilateral law with three-dimensional deformation data.The horizontal and vertical strains of Wenchuan are calculated with the three-dimensional GPS data during 2005 to 2008.The results show that the horizontal principal strains of Wenchuan and Yingxiu are extrusion.The main vertical principal strain is positive in the southeast direction,but it is negative in the northwest direction.The main vertical principal strain is consistent with the observation that the surface is sinking in the southeast and uplifting in the northwest.The maximum principal strain is in Y（east）direction.The maximum shear strain is in XY（northeast）direction.Wenchuan is situated on the high gradient of the principal and shear strains,coinciding with the location of the earthquake.