关键词: 汶川M_S 8.0地震, 逆断层, 水平缩短量, 探槽

Abstract: A reasonable and authentic estimate of surface rupture shortening amount of reverse fault is essential to a thorough understanding of the co-seismic surface deformation parameters,while we have no effective or feasible methods to deal with it,presently.The paper attempts to analyze and calculate horizontal shortening amounts of reverse fault with trench excavation basing on the investigations of the surface ruptures of the M_S 8.0 Wenchuan earthquake.On this condition,we conclude three genesis models of fault scarp,namely,faulting,flexuring,and superposition of faulting and flexuring.The paper proposes several calculation methods about horizontal shortening amounts of reverse fault based on these fault scarp models,and also gives detailed mathematic proof and constraint factors when considering complicated phenomena.Moreover,combined with these models,we discuss how to correctly apply and interpret the reverse surface rupture information revealed by trench.Finally,we demonstrate the calculation process and results of the reverse fault's horizontal shortening amounts in the trench close to the Central School of Bailu and the trench at Quanxin village of Hanwang,which are(2.83?0.3)m and(0.61?0.11)m,respectively.

Key words: M_S 8.0 Wenchuan earthquake, reverse fault, horizontal shortening amount, trench