Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 48, Issue 7, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2020GL091757
Keywords
cascade of earthquakes; ETAS; foreshock; low completeness catalog; mainshock nucleation; Southern California
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Funding
- European Research Council (ERC, under the European Union's Horizon 2020 research and innovation program) [805256]
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Research suggests that not all mainshocks in Southern California are preceded by significantly elevated seismic activity, making anomalous foreshock activity relatively uncommon. Testing against a model, only a few mainshocks exhibit mainshock-specific anomalies with high predictive power.
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.
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