北天山地区2011年以来两次6级地震前的地震学中短期异常特征

Mid-and short-term anomaly characteristics on seismicity before the Two M6. 0 earthquakes in northern Tianshan Mountains since 2011

通过分析北天山地区历史强震、构造活动背景、区域应变能积累特征以及2011年11月1日尼勒克、巩留交界6.0级和2012年6月30日新源、和静交界6.6级地震前区域地震活动异常特征等,探讨了这两次6级地震前的地震学中短期异常特征。结果表明,2011年6月以来北天山地区中强以上地震处于加速活动状态,进入应变能释放阶段;尼勒克、巩留交界6.0级和新源、和静交界6.6级地震震前先呈6级地震平静而后被打破、中强地震成组活动和空间迁移、条带和空区等较明显的中期异常;震前还出现了较为相似的4级以上地震围空和5级逼近地震,且逼近地震与主震发生时间间隔均为14天,显示了较清晰的异常图像和较明显的中短期震兆特征。

By analyzing historical strong earthquake activity,tectonic activity background,regional strain accumulation and anomaly character on regional seismicity before the Nilka-Gongliu Ms6.0 earthquake on November 1,2011 and the Xinyuan-Hejing Ms6.6 earthquake on June 30,2012,the article researches the mid-and short-term anomaly character on seismicity before the two Ms 6.0 earthquakes.The result shows that moderately strong earthquake activity in the northern Tianshan mountains appeared accelerated since June,2011,and entered into the strain energy release stage.There are obvious mid-term anomalies such as Ms6.0 earthquake quiescence and broken,grouping activity and space migration of moderately strong earthquakes,seismic belt and gap etc.before the 2011 Nilka-Gongliu Ms6.0 earthquake and the 2012 Xinyuan-Hejing Ms6.6 earthquake.There appeared M ＞ 4.0 earthquake gap and imminent earthquake with the magnitude 5.0 before the two earthquakes,and the time intervals between the imminent earthquakes and the mainshocks were both 14 days or so,and which shows the clear abnormal images and mid-and short-term anomaly character.