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大强固区之间的相互作用和震后运动可以引起触发,强固区破裂引起相邻强固区加载。震后运动可以在大范围内发生并引起相邻区域的不均匀应变积累。观测表明大震后首先发生中等地震的地点正好是下次大震的位置,所以任何一个大地震发生都提供了一个探寻临界破裂区的良好时机。依据1960—1980年资料总结的中期地震危险性估测方法称为“诱发前震图象”,1981—1992年的地震资料完全证实了该方法的可靠性。 相似文献
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The aim of this work is to quantitatively set up a simple hypothesis for occurrence of earthquakes conditioned by prior events, on the basis of a previously existing model and the use of recent instrumental observations. A simple procedure is presented in order to determine the conditional probability of pairs of events (foreshock-mainshock, mainshock-aftershock) with short time and space separation. The first event of a pair should not be an aftershock, i.e., it must not be related to a stronger previous event. The Italian earthquake catalog of the Istituto Nazionale di Geofisica (ING) (1975–1995, M 3.4), the earthquake catalog of the Japan Meteorological Agency (JMA) (1983–1994, M 3.0) and that of the National Observatory of Athens (NOA) (1982–1994, M 3.8) were analyzed. The number of observed pairs depends on several parameters: the size of the space-time quiescence volume defining nonaftershocks, the inter event time, the minimum magnitude of the two events, and the spatial dimension of the alarm volume after the first event. The Akaike information criterion has been adopted to assess the optimum set of space-time parameters used in the definition of the pairs, assuming that the occurrence rate of subsequent events may be modeled by two Poisson processes with different rates: the higher rate refers to the space-time volume defined by the alarms and the lower one simulates earthquakes that occur in the nonalarm space-time volume. On the basis of the tests carried out on the seismic catalog of Italy, the occurrence rate of M 3.8 earthquakes followed by a M 3.8 mainshock within 10 km and 10 days (validity) is 0.459. We have observed, for all three catalogs, that the occurrence rate density for the second event of a couple (mainshock or aftershock) of magnitude M2 subsequent to a nonaftershock of magnitude M1 in the time range T can be modeled by the following relationship: (T, M2) = 10a + b(M1 - M2) with b varying from 0.74 (Japan) to 1.09 (Greece). The decrease of the occurrence rate in time for a mainshock after a foreshock or for large aftershocks after a mainshock, for all three databases, obeys the Omori's law with p changing from 0.94 (Italy) to 2.0 (Greece). 相似文献
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针对2011年日本东北大地震(Tohoku-Oki地震)发生前后较短时间内的多次较大前震和余震和主震混在一起,不利于提取出主震同震信号的问题,该文利用弹性位错理论模拟计算了Tohoku-Oki地震一次较大前震和两次较大余震的同震重力变化,讨论了这3次地震单独和综合的重力效应,并与主震重力变化对比分析,认为这3次前震和余震引起的重力变化数值较大,影响范围广,会直接影响到Tohoku-Oki地震主震的同震重力信号提取,所以需要作为重要误差考虑。 相似文献
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1999年辽宁省岫岩5.4级地震的临震预报及其地震活动研究 总被引：3，自引：0，他引：3
１９９９年１１月２９日１２日１０分（北京时间）,中国辽宁省岫岩地区发生一次５．４级地震。这次地震前,在震区记录到丰富的中小地震活动,组成了完整的地震系列。该系列具有小震频度随时间增多,震级上升,ｂ值较低,地震位置集中和地震Ｐ波被动一致,将其判断为震前系列,并抓住了前震活动从密集突然变为相对平静这一大震即将发生的特征,作出了临震预报,于１１月２８日晚入震意见通报给辽宁省地震局有关部门。这次地震的预报 相似文献
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2021年5月21日漾濞发生MS 6.4地震,震前地震活动异常明显,中长期阶段云南地区3级地震活动水平较低,滇西北地区出现长达456天的4级地震平静;短临阶段震中区附近出现3—4级地震条带;临震阶段中小地震活动由外围地区开始向震中区迁移,震中区出现直接前震。 相似文献
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