From Small The Yudong Surface Rupture Of The Kinetic Mechanism Of The Wenchuan Earthquake

The serious earthquake had been taken place in Sichuan province at 2:28 p.m on May 12,2008. Epicenter is located in Yingxiu town nearby and the depth of earthquake focus is about 10-20km. The process lasted 120 seconds and main fracture process lasted 90 seconds. Wenchuan earthquake is the type of thrust of inner plate. It provides an opportunity for studying geometric shape of fracture and dynamic procedure. Also, it has important meaning for studying and building dynamic theory model.Xiaoyudong fault is located between Beichuan-Yingxiu fault and Guanxian-Anxian fault. The paper studies the value of the type variable of Xiaoyudong bridge and adjacent area, characteristic of surface rupture zone. It analyses mobility of Xiaoyudong fault. The characteristic of motion is different from Longmenshan fault zone and it is left-lateral fault. Surface rupture characteristic of cobblestone street where is north of Xiaoyudong bridge and use condition of street indicate that fracture exists in Xiaoyudong area and Xiaoyudong fault has already existed there but doesn't appear in surface.Based on structural stratigraphic geology principal and characteristic of stratigraphic record, Longmenshan tectonic zone is divided into western tectonic zone, middle tectonic zone and eastern tectonic zone.This paper studies surface rupture characteristic, tectonic geology characteristic and crust-mantle geometric construction characteristic of Longmenshan fault zone.By means of geophysic technical data, the characteristic of crust-mantle of Longmenshan tectonic zone is obtained, including electrical property structure, velocity structure, abnormal characteristic of Bouguer correction and density structure. Lithosphere of Longmenshan orogenic zone which is next to Songpan-Ganzi fold zone exists two low resistance and low velocity layers, making up double slide layer which is passage way of substance of lower crust and upper mantle. Deep crust-mantle substance decouples with shallow crust substance by low velocity layer of upper and middle curst.Combined with decoupling relationship of deep and shallow crust-mantle substance, mobility of wenchuan earthquake, powerful middle-latitudinal force effect to the movement of crust-mantle substance, incentive of wenchuan earthquake and its dynamic mechanism are discussed in this paper.