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

摘要： 2010年4月14日在青海省玉树县发生了M_S7.1地震,形成了长达65km的地表破裂带,甘达村西D1、果庆益荣松多D2是地表破裂带上破裂特征具代表性的2个地点。这2个地点的同震地表破裂特征调查结果显示:1)破裂沿先存的断裂晚第四纪活动遗迹展布,在甘达村西主要表现为张剪切破裂呈雁列状展布,在不连续的岩桥区分布了挤压鼓包,地表破裂带主要集中在古地震坳槽中,通过测量一个错断的围墙得到该点的位错量为1.4m;2)在果庆益荣松多,山前坡积物中展布的破裂带由斜列距约30m的次级破裂右阶斜列组成,而次级破裂则由一系列斜列距3～5m的单条破裂右阶斜列组成,单条破裂主要表现为挤压鼓包-张裂缝相间排列与裂缝带等2种破裂样式,在河谷中则表现为挤压垄脊和陷落塘,实测栅栏位错量为1.3m;3)破裂整体为左旋走滑性质,未见明显垂直错动分量,破裂样式为典型的走滑破裂特征,地表破裂带沿先存断错地貌分布,反映晚第四纪活动的甘孜-玉树断裂是此次地震的发震断裂,该断裂大震活动具有原地重复发生的特点。

关键词: 玉树M_S7.1地震, 地表破裂, 甘孜-玉树断裂