自2019年正式运行以来,震后趋势判定技术系统CAAFs为震后应急与趋势研判及时提供数据和技术支撑。本文梳理总结CAAFs系统持续4.5年产出的数据,从全国和不同地区两个方面评价系统产出的震后余震预测结果,得到以下三点认识:①震级上限预测(发生某震级以上地震的可能性不大)的正确率大多为90 %及以上,显著优于震级区间预测(存在发生同等大小地震的可能或存在发生某震级左右地震的可能),各分区预测情况差异不大; ②震级区间预测震级普遍比地震实况偏高,实际7日内发生的最大余震震级与预测震级的差值(震级偏差)落入[-0.5,0.5]区间的地震比例约为44 %,落入[-1,1]区间的地震比例约为69 %,越靠近[-0.5,0.5]区间,地震的比例越高; ③震级区间预测中,各分区有一定差异,西南地区优于西北、华南和华北东北三个地区,总的来看4~5级地震预测情况不如其他震级区间,可能与该震级区间内地震的最大余震震级变化范围较大有关。

Since official operation in 2019,CENC Automatic Aftershock Forecasting System(abbr. CAAFs) has provided both timely data and technical support for post-earthquake emergency responses and post-earthquake trend analysis. This article summarizes the data output of the CAAFs for 4.5-year operation,and evaluates the aftershock prediction results produced by the system from both national and regional areas. Our results show that:①the accuracy of upper-limit earthquake magnitude prediction (i.e. the happening probability of earthquakes with a certain magnitude or above is not high) is mostly ≥ 90 %,which is significantly better than the interval earthquake magnitude prediction(i.e. the happening possibility of earthquakes with the same magnitude or a certain magnitude occurring with an error of ±0.5). There is not much difference in the predicted results in different seismic zones; ②The predicted magnitudes in the interval are generally higher than the actual earthquake magnitude values. The proportion of earthquakes with magnitude deviation(actual maximum aftershock magnitude within 7 days minus predicted magnitude)falling into[-0.5,0.5] is about 44 %,falling into[-1,1] is about 69 %. The closer the magnitude deviation is to the[-0.5,0.5] interval,the higher the proportion of earthquakes are; ③The result of interval prediction in southwestern China is better than that in the northwestern,southern,and north-northeastern China. The predicted results of M4.0~5.0 earthquakes are not as good as those of other magnitude ranges,which may be related to the large range of changes in the maximum aftershock magnitude of earthquakes in this magnitude range.

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中国地震局震情跟踪项目(2024020502)资助