On the Relationship between the Omori and Gutenberg–Richter Parameters in Aftershock Sequencesстатья
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Дата последнего поиска статьи во внешних источниках: 25 ноября 2020 г.
Аннотация:The issues concerning the relationship between two self-similarity parameters—the Gutenberg–Richter b- and Omori p-values—in the aftershock sequences are explored. In the laboratory experiments,under fracture initiation in the rock by sharp jumps in the axial stress, a correlation between the p- and b-values isrevealed in the fracture relaxation regimes similar to aftershocks. The correlation observed in the experimentson water-saturated sandstone samples with the preliminarily formed faults is negative and clearly pronounced.The correlation in the case of dry samples of migmatite and concrete proved to be positive but itsstatistical significance is lower than for the wet samples. The analysis of the literature data on detecting theconnection between parameters p and b in the natural aftershock sequences shows that the reported resultsare heterogeneous. Some authors conclude that these parameters are connected and that both positive andnegative correlation is noted between them. Other authors present evidence suggesting the absence of any correlation.Our study of the natural aftershocks based on the data of regional earthquake catalogs has shown thatthe statistical estimates of the Gutenberg–Richter and Omori parameters are fairly sensitive to the quality andhomogeneity of the input data. The key factors affecting the estimation quality of these parameters are established,and the procedure for selecting the aftershock catalogs for subject analysis is developed. The results ofstatistical estimating the Gutenberg–Richter and Omori parameters in the aftershock processes in the regionswith different types of the tectonic regimes—subduction zones and regions of shear transform faults—haveshown that that the correlation of these parameters in the subduction zones can be positive and negativeeither. In the zones of the transform faults, the connection between these parameters is not detected. Ourstudy generalizes K. Scholtz’s idea that the Omori law can be explained by the superimposition of the relaxationprocesses having different relaxation times. According to the generalized model, the different sign of thecorrelation between the self-similarity parameters in the aftershock processes correspond to the differentrelaxation mechanisms with different types of the dependence of the relaxation time on the “size” of therelaxator. It is currently unclear which particular mechanisms are implemented in the aftershock processes.The relationship between the Omori and Gutenberg–Richter parameters revealed by our laboratory experimentsand field studies (positive correlation, negative correlation, or lack of correlation) may indicate theimplementation of different relaxation mechanisms in some or other particular conditions.