Abstract: On April 14, 2010, a devastating M_S7.1 earthquake happened in Yushu County, Qinghai Province. Field geological investigation and remote sensing interpretation show that this earthquake generated an inverse L-type surface rupture of about 50 km, with a maximum displacement of no less than 1.3 m. The surface rupture can be divided into three parts: We found no obvious rupture traces for a long distance of 16km between the northern and middle part; the middle and the southern part showed a left-step arrangement, local features of each part presented a characteristic of right-step pinnate arrangement. The seismogenic Yushu fault is dominated by strike-slip motion, with a small amount of reverse component. Differential movement between the southern Qiangtang block and northern Bayankala block caused this earthquake. Earthquake recurrence period is 185~108 a. Along an approximately 20 km part of Ganzi-Yushu fault, between the southern surface rupture of Yushu M_S7.1 earthquake and the 1896 earthquake, no surface rupture has been found, its seismic risk needs further research.

Key words: Yushu M_S7.1 earthquake, Surface rupture, Coseismic displacement, Sinistral strike-slip, Recurrence interval