THE SURFACE RUPTURES AND THE MACROSCOPICAL EPICENTER OF YUSHU M_S7.1 EARTHQUAKE

At 7: 49: 40.7 on April 14,2010,a MS 7.1 earthquake happened in Yushu County of Qinghai Province.In the field investigation two surface rupture zones were observed from west to east,Longbaotan surface rupture zone and Yushu surface rupture zone.They display NW trending and are respectively developed along hang wall of the Longbaotan active fault and Yushu active fault at an interval of 22km.The Longbaotan surface rupture zone,trending along 290° with a length of 21.5km,was sinistral strike-slip movement with a sinistral strike-slip displacement of about 1m.The Yushu surface rupture zone,trending 310° with a length of 23km,can be further divided into three sections.It shows sinistral strike-slip movement in western and middle segment,sinistral strike-slip and thrust in eastern segment.The maximum sinistral strike-slip displacement(2.4m) of the rupture zones appears near the Guoyangyansongduo.According to the displacement of the earthquake surface rupture and building destruction,the earthquake macroscopical epicenter can be considered in the Guoyangyansongduo near the macroscopical epicenter coordinates: at 33°03′11″N and 96°51′26″E.