Foreshock Rates from Aftershock Abundance
Foreshock Rates from Aftershock Abundance
复制标题
余震强度与前震发生率
DOI：
10.1785/0120060143
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发表时间：
2008
影响因子：
3
通讯作者：
Euan Smith
中科院分区：
文献类型：
--
作者：
A. Christophersen;Euan Smith
前震是否表现得像主震那样，恰好有较大的余震，这个问题对于理解地震成核和地震丛集的模拟是很重要的。许多模型，包括预测加州短期地震危险性的短期地震概率（STEP）模型和描述地震丛集的地震型余震序列（ETAS）模型，都认为包括前震在内的所有M级地震都能触发地震，触发能力为10 αM。根据震级-频率分布的古腾堡-里克特关系，触发地震的震级与10- bM成正比，因此可能大于初始事件的震级。然而，许多研究观察到前震发生率低于余震模型的预测。在这篇文章中，我们表明，对于均匀的地震目录和前震和余震的一致定义，前震率可以预测的余震特征。对于南加州，震级范围为2.0-4.5的地震群的初始事件之后在一天内至少发生一次较大事件的概率约为4%。这与来自全球质心矩张量（CMT）目录的相应数据一致，其中一个集群的初始地震在30天内至少发生一次较大事件的概率约为3%。这些前震率显着低于以前的报道，我们讨论了可能的原因。
The question whether foreshocks behave like mainshocks that happen to have larger aftershocks is important for the understanding of earthquake nucleation and the modeling of earthquake clustering. Many models, including the short-term earthquake probability (STEP) model, for forecasting short-term earthquake hazard in California, and the epidemic-type aftershock sequence (ETAS) model, for the description of earthquake clustering, imply that all earthquakes of magnitude M , including foreshocks, can trigger earthquakes according to a magnitude dependent triggering ability 10 αM . The magnitudes of the triggered earthquakes are proportional to 10- bM , according to the Gutenberg–Richter relation for the magnitude-frequency distribution, and therefore can be larger than the magnitude of the initiating event. However, numerous studies observe a lower foreshock occurrence than predicted from aftershock models. In this article we show that, for homogeneous earthquake catalogs and a consistent definition of foreshocks and aftershocks, foreshock rates can be predicted from aftershock characteristics. For Southern California the probability that the initiating event of an earthquake cluster in the magnitude range 2.0–4.5 is followed by at least one larger event within one day is around 4%. This agrees well with corresponding data from the global centroid moment tensor (CMT) catalog where the probability that the initiating earthquake of a cluster is followed by at least one larger event within 30 days is around 3%. These foreshock rates are significantly lower than previously reported, and we discuss possible reasons for this.