宁夏及邻区5级以上地震前中等地震活动增强特征研究

STUDY ON CHARACTERISTICS OF THE SEISMICITY ENHANCEMENT OF MODERATE EARTHQUAKES BEFORE M≥5 EVENTS IN NINGXIA AND ITS ADJACENT AREAS

通过对 1 96 5年以来宁夏及邻区ML ≥ 5.0以上地震前中等地震资料的分析 ,发现大多存在中等地震活动增强特征 .在A区中等地震活动增强异常结束后 7个月内发生 5级地震的概率为 0 .71 ;B区在 3年内发震概率为 0 .6 0 .发震地点位于异常分布范围的外围连线附近的概率为 0 .79.其预测效能R值评分为 0 .75.因此中等地震活动增强可以作为本区 5级以上地震的一种中期预测方法 .

Through analysising the seismicity data before M L ≥5.0 earthquakes in Ningxia and its adjacent areas since 1965,it is found that there mostly is the characteristics of enhancement of moderate earthquakes before M L ≥5.0 earthquakes.In A part of the study area,the probability for occurrence of M L ≥5.0 earthquake is 0.71 after anomaly of the enhancement of moderate earthquakes in 7 months;and it is 0.60 in 3 years in B part.The probability that earthquake locats near the outer linked lines of all earthquakes in one enhancement of moderate earthquakes is 0.79.Its R value is 0.75.So the enhancement of moderate earthquakes can be a middle period prediction method for M≥5 earthquake in this region.