Abstract
It has been emphasized that the temporal occurrence of earthquakes in various spatial areas and over ranges of magnitude may be described by a unique distribution of inter-earthquake intervals under suitable rescaling, implying the presence of a universal mechanism governing seismicity. Nevertheless, it is possible that some features in the fine temporal patterns of event occurrences differ between spatial regions, reflecting different conditions that cause earthquakes, such as relative motion of tectonic plates sharing a boundary. By abstracting the non-Poissonian feature from non-stationary sequences using a metric of local variation of event intervals Lv, we find a wide range of non-Poissonian burstiness present in the temporal event occurrences in different spatial areas. Firstly, the degree of bursty features in the occurrence of earthquakes depends on spatial location; earthquakes tend to be bursty in areas where they are less frequent. Secondly, systematic regional differences remain even if the overall correlation between burstiness and the rate of event occurrence is eliminated. Thirdly, the degree of burstiness is particularly high on divergent tectonic boundaries compared to convergent and transform boundaries. In this way, temporal patterns of event occurrences bear witness to the circumstances underlying event generation.
Highlights
The present analysis has revealed that non-Poissonian burstiness in temporal sequences of earthquakes depends on spatial location and the type of tectonic boundary
The systematic dependency of the temporal burstiness on spatial area seems to contradict the previous belief that earthquake recurrence times are universal
Cv, which measures the ratio of the standard deviation of intervals to the mean, but Cv does not efficiently detect differences among spatial areas (see supplementary data)
Summary
Our analysis is based on the global catalog of NEIC-PDE, which includes information about the time, spatial coordinates and magnitude of earthquakes. We adopted data from 1 January 1973 to 31 December 2009, during which a total of 530 481 earthquakes were recorded. Our analysis is based on the global catalog of NEIC-PDE, which includes information about the time, spatial coordinates and magnitude of earthquakes.. To avoid problems arising from missing data for smaller earthquakes, we considered only events with a magnitude above the threshold M = 4.5, above which the cumulative number of earthquakes obeys the Gutenberg–Richter law [18]. Every earthquake of a magnitude higher than the threshold was regarded as a unit event, regardless of whether it would be classified as a mainshock or an aftershock [8,9,10]. We collected earthquake events occurring in each cell, while ignoring spatial information, such as location within a cell and the depth of the hypocenter. The areas adopted under these conditions were assembled along the boundaries of tectonic plates [15]
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