Moutote L, Marsan D, Lengliné O, Duputel Z
Institut Terre et Environnement de Strasbourg UMR7063 Université de Strasbourg/EOST CNRS Strasbourg France.
Institut des Sciences de la Terre UMR5275 Université Savoie Mont Blanc CNRS Le Bourget du Lac France.
Geophys Res Lett. 2021 Apr 16;48(7):e2020GL091757. doi: 10.1029/2020GL091757. Epub 2021 Apr 7.
Earthquakes preceding large events are commonly referred to as foreshocks. They are often considered as precursory phenomena reflecting the nucleation process of the main rupture. Such foreshock sequences may also be explained by cascades of triggered events. Recent advances in earthquake detection motivates a reevaluation of seismicity variations prior to mainshocks. Based on a highly complete earthquake catalog, previous studies suggested that mainshocks in Southern California are often preceded by anomalously elevated seismicity. In this study, we test the same catalog against the Epidemic Type Aftershock Sequence model that accounts for temporal clustering due to earthquake interactions. We find that 10/53 mainshocks are preceded by a significantly elevated seismic activity compared with our model. This shows that anomalous foreshock activity is relatively uncommon when tested against a model of earthquake interactions. Accounting for the recurrence of anomalies over time, only 3/10 mainshocks present a mainshock-specific anomaly with a high predictive power.
大型地震之前发生的地震通常被称为前震。它们常被视为反映主破裂成核过程的前兆现象。这种前震序列也可以用触发事件的级联来解释。地震探测的最新进展促使人们重新评估主震之前的地震活动变化。基于一个高度完整的地震目录，先前的研究表明，南加州的主震之前往往伴随着异常高的地震活动。在本研究中，我们用考虑了地震相互作用导致的时间聚类的流行型余震序列模型来检验同一个目录。我们发现，与我们的模型相比，53次主震中有10次之前出现了显著增强的地震活动。这表明，在根据地震相互作用模型进行检验时，异常的前震活动相对不常见。考虑到异常随时间的反复出现，只有3/10的主震呈现出具有高预测能力的特定主震异常。
