跨断层形变测量异常特征分析

Analysis of the Anomaly Characteristics from Cross-fault Deformation Measurements

在统计近40年我国强震前跨断层形变异常的基础上,对异常持续时间、异常空间分布、异常幅度特征及它们之间的关系进行了分析,讨论了跨断层形变观测异常特征和监测不同震级地震跨断层场地的最大间距及观测周期。结果表明：异常主要以中短期和中期异常为主,尤其在震前1年内异常最多;异常持续时间与震级呈正比例的关系;异常在空间分布上有随震级增大而扩大的现象;异常幅度有随异常持续时间增大而增大的趋势;震中距在160～350 km范围内异常幅度较大;异常形态主要分为趋势型和突变型两种。监测不同震级的地震跨断层形变场地间距可以不同,监测7级地震形变场地间距应小于450 km;6级应小于300 km;5级应小于200 km;4级应小于100 km。跨断层形变观测周期应不大于3个月。

Based on the statistics of cross-fault deformation anomalies before strong earthquakes during the last forty years,this article analyses the characteristics of the time duration,spatial distribution,amplitude of the anomalies and the relationship of all the three factors.it disgusses the anomaly characteristics of the measurement of cross-fault deformation as well as the maximum spacing of the cross-fault sites and observation cycle of the monitoring of different magnitude of earthquakes.The results suggest that： The anomalies are mainly of medium term as well as short and medium terms,occur more frequently one year before the earthquakes.The time duration of the anomalies is directly proportional to the earthquake magnitude.The spatial distribution of the anomalies also has a phenomenon that it extends as the augment of the epicenter distance.The amplitude of the anomalies enlarges with the increase of time duration and reaches to higher level when the epicenter distance is within 160 to 350 km.The anomaly shape is devided into two main types：trend and mutant.The spacing of monitoring cross-fault sites of different earthquake magnitude can be different： The spacings for monitoring magnitude 7 earthquakes should be less than 450 km,and 300 km,200 km,100 km for magnitude 6,5,4 earthquakes respectively.The measurement cycle is supposed to be within three months.