Tectonic background of the Ms 7.4 earthquake at Yutian on March 21,2008

There is a M7.4 earthquake at the boundary of Yutian and Qira County in Hotan Prefecture, Xinjiang,China,on March 21,2008.The earthquake occurs in the south of Tarim Basin and near the Altyn Tagh earthquake zone at the edge of West Kunlun Mountain.The southwest of Altyn Tagh earthquake zone displays the structure with three branches,widening towards west.The north branch distributes at the Xiaoerkule Basin.The middle branch,which is the main fault structure of this earthquake,distributes at the Ashikule Basin.The south branch,which limited the extension of aftershock,reaches to Gozha Co Basin.The rupture of this earthquake is mainly tense with strike-slip function.It is dip-slip rupture which is the result of left-lateral dislocation Altyn deep fault.This is consistent with the focal mechanism solutions.The strong seismic activity in the Altyn fault usually goes with the activity in the main fault zone around Tibet plateau.A M8.0 earthquake occurs at Wenchuan in Sichuan just after it more than one month.It is noticeable that whether the seismic activity will be strengthened in Tibet plateau or at the edge of it,also in the west of Tarim Basin in Xinjiang and around the Pamir plateau.