关键词: 玉树M_S7.1地震, 地表破裂, 甘孜-玉树断裂

Abstract: The M_S 7.1 Yushu,Qinghai earthquake on April 14th,2010 generated a surface rupture zone about 65km long.The west of Ganda Village,D1,and Guo Qing Yi Rong Song Duo,D2,are the two most representative places of surface rupture characteristics of the M_S 7.1 earthquake in Yushu,Qinghai Province.Survey results on co-seismic surface rupture characteristics at the two locations show that:(1)Surface rupture extends along the remains of late Quaternary activities on the pre-existing fault,and at the west of Ganda Village,the surface rupture is composed of tensile shear fcractures arranged en echelon,with mole tracks.Most part of the surface rupture is distributed along the paleoseismology trench,and through measuring an offset wall,we get the offset of 1.4m.(2)At Guo Qing Yi Rong Song Duo,the surface rupture zone consists of a series of right-step en echelon sub-cracks with a spacing about 30m each other,and the sub-crack is formed by the right step cracks,with a spacing of 3～5m.The mole track-tension crack and crack belt compose the single rupture,which are along the slope wash in front of the mountain.The surface rupture across the river valley appears as compressional ridge and sag pond in the valley.The offset of a fence is measured to be 1.4m.(3)The surface rupture shows left-lateral strike-slip characteristics,with no significant vertical component.The surface rupture mode shows a typical strike slip character.The surface rupture distributed along the pre-existing offset landforms reflects that the Ganzi-Yushu Fault,which is an active fault of Late Quaternary,is the seismogenic fault of this earthquake.The fault has the character of in situ recurrence of large earthquakes.

Key words: The M_S 7.1 Yushu earthquake, surface rupture, Ganzè-Yushu Fault