Low significance of foreshock activity in Southern California

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Authors

Luc Moutote , David Marsan, Olivier Lenglin√©, Zacharie Duputel

Abstract

Earthquakes preceding large events are commonly referred as foreshocks. They are
often considered as precursory signals 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 is a motivation to re-evaluate seismicity variations prior to mainshocks. Based on a highly complete earthquake catalog, Trugman and Ross (2019) and van den Ende and Ampuero (2020) suggested that mainshocks in southern California are often preceded by anomalously elevated seismic activity. These studies assume a time-independent seismicity and thus neglect earthquake interactions. In this study, we test the same catalog against the Epidemic Type Aftershock Sequence model that accounts for earthquake clustering. We find that less than 5 out of 53 selected mainshocks (10%) are preceded by significantly elevated seismicity rates. This suggest that foreshock observations can generally be explained by background seismicity and by cascades of earthquakes even in highly complete earthquakes catalogs.

DOI

https://doi.org/10.31223/X5130R

Subjects

Geophysics and Seismology

Keywords

Foreshocks, Southern California, ETAS, mainshock nucleation, cascade of earthquakes, low completeness catalog, Southern California, ETAS, Mainshock Nucleation, Cascade of earthquakes, Low compteness catalog

Dates

Published: 2020-11-20 08:28

Last Updated: 2020-11-20 16:28

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

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