Focal Characteristics of M_S≥7.7 Earthquakes in Xinjiang and its Adjacent Areas

We analyse the type of earthquake sequence,seismogenic tectonic and focal signatures,and dynamic evolution characteristics of seismic pattern in the period of earthquake preparation with strong MS≥7.7 earthquake in Xinjiang and its adjacent areas.In the meantime,we make comprehensive study of the focal characteristics of strong earthquakes.The preliminary results show that the strong earthquake sequences are diverse,including main-after shock type,isolated type and double earthquake type.The rupture characteristics of strong earthquakes basically reflect the tectonic movement characteristics of the Tianshan tectonic belt,which is mainly thrust behavior,while Altay tectonic belt is mainly strike-slip.The evolution characteristic of seismic pattern is obvious in the stage of earthquake preparation.During long and medial period MS6.0 earthquakes are active,in the medium-term earthquakes are relatively quiet and activity of earthquakes differ in the short-term.The seismic activity of Xinjiang is significantly quiet after strong earthquakes,the activity in different sizes all reflects the migration regularity that is from southwest to northeast.The main power source of strong earthquakes in Xinjiang comes from the northward pushing of the Indian plate.