关键词: 汶川M_S8.0地震, 地表破裂带, 雁行阶区, 震害意义, 汉旺镇

Abstract: The epicenter intensity of the M_S 8.0 Wenchuan earthquake of 12^th May 2008 is Ⅺ.Hanwang town,Mianzhu county,Sichuan Province,located on the edge of seismic intensity Ⅹ zone,suffered the seismic intensity one degree higher than the surroundings,in the respects of both the houses damaged or the number of victims and missing persons,as close to the destruction in meizoseismal region.In this paper,the distribution pattern of the earthquake surface rupture zone around Hanwang town is discussed,focusing on the causes for the aggravation of seismic damage.The paper introduces two left-step en echelon surface rupture zones,which are 1.5km apart,located at the north and south of Hanwang town.The one on the north of Hanwang town has a vertical displacement of 1.4m and horizontal dextral displacement 0.44m,respectively.The other on the south of Hanwang town has a vertical displacement of 3.0～0.2m,descending from west to east.Although the two surface rupture zones did not pass through the center of the town,since Hanwang town is located right in the sinistral stepover clamped by the two surface rupture zones,the buildings in the stepover were subject not only to the vibration from the seismic source but also the compression inside the stepover,thus aggravating the damage of the buildings in Hanwang town.This also shows the diversity of building damage by the surface rupture zone.The seismic damage of Wenchuan earthquake around Hanwang town shows that the stepover of the surface rupture zone is also the special structural part subject to aggravated damage in earthquake.

Key words: Wenchuan M_S8.0 earthquake, surface rupture zone, en echelon stepover, significance of seismic damage, Hanwang town