INVESTIGATION ON WIDTHS OF SURFACE RUPTURE ZONES OF THE M 8.0 WENCHUAN EARTHQUAKE,SICHUAN PROVINCE,CHINA

The 12 May 2008 Wenchuan Earthquake created about 240km-long surface fault ruptures along the Central Fault and about 72km along the Mountain Front Fault,two of the three sub-parallel secondary faults of Longmenshan thrust faults striking NE-SW,according to field investigation of surface faulting.From north to south,most of the widths of intense surface rupture zones are less than 40m,and above 1/2 are between 10～30m.Many buildings along fault surface ruptures were destroyed,including those with frame structure or reinforced concrete structure,and we also find some houses or buildings have withstood the strong earthquake and its aftershocks for their excellent performance of earthquake-resistance.The distance between fault scarps and the buildings are from 10 to 30 meters.Based on the field investigation,on the widths of surface rupture zones of historical strong earthquakes,and considering crustal shortening for inverse faulting and other various uncertainties,it is suggested that safety distance away from active fault in rebuilding is 25m.Within this distance,only one or two-storeyed buildings with higher standard of earthquake-resistance can be constructed,and public buildings,like schools and hospitals should be prohibited to build.