The purpose of this paper is to characterize the statistical distribution of worldwide largest earthquakes. We analyze the distribution of worldwide shallow events with M s 7.0+ since 1900, by following the Occam's razor philosophy; we start from the simplest possible model (stationary Poisson process), and we inspect more complicated models only if the data show significant departures from the simplest one. The results show two important characteristics; first, worldwide M s 7.0+ earthquakes tend to cluster in time and space, with features similar to smaller events. Second, for some seismic regions there is evidence in favor of long-term fluctuations of the earthquake rate. These results support the hypothesis of universality, suggesting that an ETAS model with a background varying with time can be considered reliable to describe the seismicity distribution over a wide space-time-magnitude window. From a practical point of view, our findings suggest that the paradigm that seismic zones are stationary systems, implicitly assumed in seismic hazard assessment, should be regarded with caution.
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机译:本文的目的是描述世界范围内最大地震的统计分布。我们遵循Occam的剃刀理念,分析了自1900年以来M s 7.0+的全球浅层事件的分布;我们从最简单的模型(平稳泊松过程)开始,并且仅当数据显示出与最简单的模型有明显差异时,我们才检查更复杂的模型。结果显示出两个重要特征;首先,全球7.0级以上的地震倾向于在时间和空间上聚集,其特征类似于较小的事件。其次,对于某些地震区域,有证据表明地震速率会长期波动。这些结果支持普遍性的假设,这表明背景随时间变化的ETAS模型可以被认为是可靠的,可以描述宽时空幅值窗口上的地震分布。从实践的角度来看,我们的发现表明,在地震危险性评估中隐含假设的地震带是固定系统的范式应谨慎对待。
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