针对年度地震危险区划定的个数问题开展了一些尝试性研究,旨在从统计学角度给出危险区个数的最佳估值,对年度地震预测实践给出一定参考意见。通过R值评分算法反推出年度地震危险区个数的估算公式,同时改进了传统聚类算法用于识别空间距离较近的地震“丛集区”,在此基础上分别统计中国大陆地区1950—2019年满足目标震级的年度地震发生个数、地震“丛集区”和“孤立发生地震”的个数之和,最后进行多种统计分布模型拟合与检验,结合置信区间确定危险区个数的合理上限。结果表明,由两种统计结果得出的年度危险区个数的参考值也略有差别,第一种基于中国大陆地区东部(107°E以东) MS5.5、西部(107°E以西) MS6.0 以上地震年度发生率的危险区个数参考值为9个,适用于稍大震级的判定; 第二种基于中国大陆地区年度 MS5.0 以上地震“丛集区”识别结果的危险区个数参考值为13个,与目前中国地震台网中心使用的个数一致,对判定年度 MS5.0 以上地震具有较好的应用实效。
In this paper,tentative studies are carried out on the number of annual seismic risk areas,aiming at giving the best estimation of which from the statistical point of view,and giving some reference to the practice of annual earthquake prediction. By R-value evaluation method formulas for calculating the number of annual earthquake seismic risk areas are deduced. Moreover,traditional clustering algorithm is improved to be used to identify earthquake “cluster” area of the close space distance. Through statistics of total number of annual earthquake,earthquake magnitude “cluster area” and “isolated earthquake” in China mainland area during from 1950 to 2019,a variety of statistical distribution models were fitted and tested to determine the reasonable upper limit of the number of risk areas. The results show that the reference values of the number of annual risk areas obtained from the two statistical results are slightly different. The first method is based on the annual occurrence rate of MS5.5 earthquakes in the east(east of 108°E) and MS6.0 earthquake in the west(west of 108°E)of mainland China. The reference values of the number of danger areas are 9,which are suitable for the determination of the magnitude of slightly larger earthquakes. The second method is based on the “cluster area” identification results of earthquakes above annual MS5.0 in mainland China,and the reference value of the number of seismic risk areas is 13,which is consistent with the number used by the China earthquake networks center at present,and is good in practical application in determining annual earthquakes above MS5.0.