Study on the source characteristics of the 2008 Ms6. 8 Wuqia, Xinjiang earthquake sequence and the stress field on the northeastern boundary of Pamir

Moment tensor solutions of 52 earthquakes occurred in the 2008 M(s)6. 8 Wuqia source region,Xinjiang,were estimated in time domain by using the long period waveforms recorded by the regional broadband stations. Then combined with the Harvard solutions, the characteristic of stress field in northeastern margin of Pamir are studied. The result reveals that overthrusting is the main pattern on the curved Kazkeaerte active reverse fault fold zone, which is located in front of the collision zone between Indian plate and Eurasian plate, as well as the northern edge of the northward bulge arc structure. And there are also a few strike-slip faults, normal fault almost does not exist. The trend of the local maximum principal stress is different on the top of the arc (the western region in the paper) and the eastern boundary (the eastern region in the paper), which is NNE and NNW respectively, suggesting the influence of clockwise rotation of Tarim block, while the whole Pamir undergoing the force of the India plate crushing to the Eurasian plate. The types of focal mechanism solutions in the southern region, which is located on the eastern section of Pamir deep seismic zone formed by intensive collision, subduction, and deformation process, are mainly strike-slip, and with some normal and reverse faults as well. The trending of the principal compressive stress in western and southern Pamir is the same, but the dip angle in western region is horizontal and the principal tensional stress in the southern region is horizontal, which may reveal that the subduction depth of the Eurasian continental lithosphere in the eastern region of central Pamir is about 150 to 170km deep and the subducting angle is about 60 degrees.