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研究我国东部9次余震序列的总体特征得到:余震频度符合 n=n_1t~(-h)关系;频度和强度随时间衰减较慢;最大地震后3、4天内发生的余震所勾划的余震区常常比最终余震区小;多数余震分布在地壳中5至10公里的深度上.一些强余震前的中小余震时空分布有下述特征:(1)强余震前几天至十几天,余震序列的频度偏离正常衰减值;(2)强余震前有中小余震震中向下一次强余震的震中附近扩展或形成空区的现象;(3)强余震前震级序列出现缺震现象;(4)余震序列有准周期性.上述特性预示其后将发生强余震,同时表明强余震有类似于大地震的孕震过程.种种现象还表明余震序列在时间和空间上可能是由主震的直接余震和强余震的次级余震相互叠加所组成的.最后将某些特性和岩石试验结果进行了比较和讨论.
The study of the overall characteristics of 9 aftershock sequences in the eastern part of China shows that the frequency of aftershocks meets the n = n_1t ~ (-h) relationship, the frequency and the intensity decay slowly with time, and the aftershocks The aftershock areas are often smaller than the final aftershock area; most aftershocks are distributed over a depth of 5 to 10 kilometers in the crust. The spatial and temporal distribution of small and medium aftershocks before some strong aftershocks has the following characteristics: (1) A few days before a strong aftershock, The frequency of aftershock sequence deviates from the normal attenuation value; (2) the phenomena of expanding or forming an empty area near the epicenter of the next strong aftershock in the epicenter before the strong aftershock; (3) the lack of earthquake before the strong aftershocks; ( 4) The aftershock sequence is quasi-periodic.The above properties indicate that strong aftershocks will occur later, and the strong aftershocks have similar seismogenic processes similar to large earthquakes.These phenomena also indicate that aftershock sequences may be composed of main shocks in time and space The direct aftershocks and the aftershocks of strong aftershocks are superimposed on each other.At last, some characteristics and rock test results are compared and discussed.