Analysis of Seismic Activity Characteristics before the Yutian MS7.3 Earthquake, Xinjiang on February 12, 2014

This paper introduces the geological structure background around the 2014 Yutian M_S7.3earthquake area,investigates and analyzes the regime of small earthquake activity and the characteristics of regional seismicity pattern in Xinjiang before the earthquake, and compares the characteristics of the regional seismic activity with the 2008 Yutian M_S7.3earthquake. The results show: 1 2 ~ 3 years before the 2014 Yutian M_S7.3 earthquake,Xinjiang was in a seismic active state with strong earthquake occurring successively,and before the 2008 M_S7.3 earthquake,Xinjiang was in the quiet state of moderate-small earthquakes with M3. 0 ~ 4. 0. 2 Before this Yutian M_S7.3 earthquake,the regional seismic activity showed a short-term anomaly feature,that is,seismicity of M ≥ 5. 0earthquakes significantly increased on the Altun seismic zone and in the source area three years before the M_S7.3 earthquake,while a five year long quiescence of seismicity of M≥4. 0 earthquakes appeared on the east of the source area in a range of about 440 km. Six months before this M7. 3 earthquake,there existed seismic gap of M3. 0 ~ 4. 0 earthquakes and near-conjugate seismic belt magnitude 3. 0 and 4. 0 in the source area. 3 The state of strong earthquake activity and the seismicity pattern of small earthquakes before this Yutian M_S7.3 earthquake were significantly different to that before the 2008 Yutian M_S7.3earthquake,and this may be related to the different seismogenic environments of the two M_S7.3 earthquakes.