将地震活动能量作为随机场，采用自然正交函数（或称经验正交函数）展开方法进行分析，计算单元取为环形，选择7级、6级地震作为样本，计算了这些7级、6级地震前环形带地震活动典型场的时间因子曲线。结果表明，选取的7级、6级地震震例震前环形带地震活动典型场的时间因子曲线明显出现了偏离正常变化的异常，异常出现时间大多在震前3年至临震时。环形带地震活动场分析方法还能够分析发生异常的空间分布情况。最后就环形带地震活动场分析方法的应用效果、参数选取以及应用于实际地震预测工作的有关问题进行了讨论。

We use the natural orthogonal function(or the empirical orthogonal function)expansion method to analyze the seismic activity energy as the random field. The calculation unit is annular,and some earthquakes with magnitude 7.0 and magnitude 6.0 have been selected as the samples. The time factor curves of the typical seismicity field in the annular zone before these magnitude 7.0 and magnitude 6.0 earthquakes have been calculated. The results have showed that the time factor curves of the typical seismicity field in the annular belt before the earthquake samples selected with magnitude 7.0 and magnitude 6.0 are obviously deviated from the normal variation. Most of the anomalies occur in 3 years before the earthquake to the imminent earthquake. The analytical method of the seismic activity field in the annular zone can also be used to analyze the spatial distribution of anomalies. Finally,the related problems about the application effect,the selection of parameters and the application in actual earthquake prediction of seismic activity field analysis method in the annular zone have been discussed.

P315

宁夏回族自治区发展和改革委员会"西部开发重点项目前期工作任务"专项资助