青藏块体东北缘跨断层形变典型震例总结与预测判据指标分析

A Summary of Cross-fault Deformations of Typical Earthquake Cases and Predictors in the Northeastern Margin of Qinghai-Tibet Block

针对青藏块体东北缘跨断层监测区及周边发生的5.8级以上地震,结合以往研究结果,对跨断层资料进行了重新梳理,重点分析了1995年永登5.8级、2000年景泰5.9级、2003年民乐—山丹6.1级和2013年岷县漳县6.6级地震前出现的跨断层形变异常。结果表明：这4次典型地震前出现的跨断层异常数量较多,为13-23项不等;分布范围较广,震中距在600km范围内,相对集中出现在300km左右范围内,也有近震区异常;异常特征以逆断加速、趋势转折、活动加剧、突跳、大幅变化等为主;震前2-3年或稍长时间开始出现异常,震前半年至1年半时段异常集中出现,具有中期背景或短期前兆意义,异常空间分布有向震中区汇聚迁移的特征。

With earthquakes above M_S5.8in cross-fault monitoring area of the northeastern margin of Qinghai-Tibet block,combined with previous research,we re-sort cross-fault data,and focus on the anomalies before earthquakes of the 1995 Yongdeng M_S5.8,the2000 Jingtai M_S5.9,the 2003 Minle-Shandan M_S6.1and the 2013 Minxian-Zhangxian M_S6.6earthquakes.The results shows that numbers of cross-fault anomalies before the 4typical earthquakes are in the range of 13-23items;abnormal wide distribution in the range of 600 km from the epicenter,relatively concentrated in the range of within about300 km,also had nearly earthquake zone anomalies.Anomaly characteristics are mainly inverse acceleration,trend turns,increased activity,jumps,and sharp changes.Anomalies began to appear 2-3years or a little longer before the earthquake,concentrated appear before the earthquake in the period of six months to one year and a half,had mid background and short-term precursory significance,and characteristics of the spatial distribution of anomalies migrated to epicenter with time.