中文摘要：

利用紫坪铺库区的GPS监测资料和都江堰市的地籍控制点的复测资料,获得同震垂直位移,并结合区内工程的破坏特征,发现都江堰段的地表破裂由三支组成：映秀段地表特征清晰,同震垂直位错为1.5～2 m;龙池段穿过龙池隧道西北端和龙溪隧道南东段,同震垂直位错约为0.8 m;紫坪铺段从库区中部通过,同震垂直位错为0.7m。三支在虹口段合并为一支,共同组成中央断裂的初始破裂段。另外,利用近断层的同震位错量获得的同震抬升量大于区域地表抬升,说明近断层存在同震位移突变的特征。

英文摘要：

The distribution of surface rupture of Wenchuan earthquake at Dujiangyan segment remains controversial for lack of direct geological evidence.We use new-collected GPS survey controlling points at the Dujiangyan reservoir and postseismic resurveyed cadastral data and combine some engineering damages in the studied area to obtain coseismic vertical displacements.The results demonstrate that the Dujiangyan surface rupture segment consists of three branches： the Yingxiu part has a clear geomorphological feature with a vertical displacement of 1.5-2 m;the Longchi part ruptured the Longchi and Longxi tunnels with a vertical displacement of about 0.8 m,the Zipingpu part passed through the Zipingpu reservoir with a uplift of 0.7 m.Finally,the three rupture parts merge into one eastward segment at Hongkou town and collectively comprise the initial rupture fault segment.In addition,regional uplift is smaller than coseismic vertical displacements along the ruptured faults,suggestive of an abrupt increase at the fault zone.