关键词: 汶川地震, 地表破裂, 同震位移, 破裂长度

Abstract: Field investigations on the 2008 surface rupture north to Shikan village show that the surface rupture is still significant in this section.The surface rupture changes its strike at the north of the town of Shikan and does not follow the previously mapped thrust which was initially considered the location the rupture traversed.Nevertheless,clear morphological expressions suggest repeated coseismic displacements along the fault trace the 2008 earthquake rupture followed.Contrast to the previous work,another 12-km-long rupture was found.It runs between Shikan town and Woqian village,trends 15°～45°,and shows thrusting with dextral slipping.The relatively large vertical and dextral strike-slip displacements of 2.1m and 3.0m respectively at Kuangpingzi do not suggest that co-seismic slip diminished gradually from a high value to a low one.The increased component of strike slip may suggest that the rupture ended as a strike-slip mode.Field observations suggest that the rupture terminates at the southwest of the Donghekou village about 20km north to Woqian village.

Key words: Wenchuan earthquake, surface rupture, coseismic displacement, length of rupture