2014年于田7.3级地震的发震构造及动力学背景的初步分析

Preliminary Analysis of Seismogenic Fault and Geodynamic Background of 2014 Yutian M_S7.3 Earthquake

2004年2月12日新疆维吾尔自治区于田县发生了MS7.3级地震,其发震断裂为阿尔金断裂带西南段的贡嘎错断裂带。由于地处高山无人区,存在区域历史地震漏记,但1970年以来5级以上地震活动是完整的,近20年来强震活动增强。综合分析认为,2008年于田MS7.3地震可能加速了本次地震的发生。根据经验统计关系估计,2014年于田地震的同震地表破裂为30—40km,最大水平位错量为1.0—1.5m,地震的复发周期为300—400年。通过阿尔金断裂上前人资料和区域构造的综合分析,认为2014年于田地震是在青藏高原向北东运动背景下左旋走滑的阿尔金断裂向南西端扩展的结果。

The 2014 Yutian Ms7.3 earthquake occurred in Yutian County,Xinjiang Uyghur Autonomous Region,on 12 Feb.2014.Its seismogenic fault is the northern Gonggacuo fault,southwest segment of the Altyn Tagh fault zone.The historical record of regional seismicity is significantly incomplete due to depopulated zone.However,the earthquake catalog of earthquakes after 1970 with magnitude greater than Ms5 is probably complete,which suggests that the activity of strong earthquakes has become stronger in the past 20 years.The 2008 Yutian earthquake may have speeded up the occurrence of this shock.Based on published data of slip rates and empirical relationships between magnitude and coseismic rupture parameters,we estimate that the surface rupture belt for the 2014 Yutian earthquake is about 30-40km long,with maximum coeismic left-lateral displacement of about 1.0-1.5m,and recurrence interval is about 300-400 years.Previous results on the Altyn Tagh fault zone and regional tectonics show that the occurrence of the 2014 shock is likely to be attributed to westward propagation at the southwest end of Altyn Tagh fault system in left-lateral strike-slip mode along the NW-striking extensional tectonic zone,due to eastward motion of the Tibetan Plateau.