Abstract: The Wenchuan earthquake(M_S=8.0)of May 12,2008 in Sichuan Province,China produced surface ruptures along the seismogenic reverse faults.It is very important to analyze the co-seismic surface ruptures quantitatively for the comprehension of tectonic behavior of the great earthquake.We discuss several issues about the quantitative analysis of co-seismic surface ruptures produced by reverse faults with some examples from Wenchuan earthquake.With the geometric relations between the parameters of deformation and survey data from planar and linear geomorphologic benchmark,solution methods for those parameters are provided.The vertical slip,horizontal dip-slip and dip angles on survey profiles were measured to calculate the actual deformation of the fault.The relationship between the apparent deformation and the real value was provided quantitatively for oblique profiles and linear benchmarks.We also made some discussions on the application of the survey data to the analysis of regional structural geometry and kinematics.

Key words: M_S8.0 Wenchuan earthquake, co-seismic surface rupture, reverse fault, deformation survey, geomorphologic benchmark

摘要： 2008年5月12日四川汶川发生M_S8.0地震,发震断裂在地表形成以逆断为主的破裂变形带。同震地表变形带的定量分析对理解地震的构造行为具有重要意义。文中以汶川地震典型调查点为例探讨了逆断型同震地表破裂变形带测量分析中值得重视并容易误解的几个问题,分析了地貌面标志和线性标志等测量数据与构造变形参数的几何关系,给出了变形参数的求解方法和相互关系。同时,就多观测点的定量数据在区域断裂几何结构变化和运动学分析中的运用进行了讨论。

关键词: 汶川M_S8.0地震, 同震地表破裂, 逆断层, 变形测量, 地貌标志