Are Foreshocks Fore‐Shocks?

Created March 24, 2026

Updated on May 7, 2026

approved

Foreshocks are spatially clustered seismic events preceding large earthquakes. Since the dawn of seismology, their occurrence has been identified as a possible mechanism leading to further crustal destabilization, hence, to major failures. However, several cases occurred without any previous anomalous seismic activity, so that the hypothesis of foreshocks as reliable seismic precursors fails to pass statistical tests. Here, we perform an all-round statistical comparative analysis of seismicity in Southern California to assess whether any differences can be identified between swarms and foreshocks. Our results suggest that extremely variable seismic patterns can forerun mainshocks, even though they tend to be preceded by clusters with more numerous events spread over larger areas than swarms and with a wider range of magnitudes. We provide a physical explanation of such dissimilarity and conclude, despite it, that foreshocks can hardly be reliable short-term precursors of large earthquakes in California.

itineris-hub
Tags:
Foreshocks
Preparatory Phases
Publication - Article
Seismic Precursors
Basic
Language
English
MainTitle
Are Foreshocks Fore‐Shocks?
Original ids
https://doi.org/10.1029/2023JB027337
Type
publication
bestAccessRight
OPEN
countries
Italy
Creator/Author
Full name
  • Davide Zaccagnino, orcid: 0000-0001-6884-8452;
  • Filippos Vallianatos;
  • Georgios Michas, orcid: 0000-0002-0284-3867;
  • Luciano Telesca, orcid: 0000-0002-5978-6031;
  • Carlo Doglioni, orcid: 0000-0002-8651-6387
Other
Description
Foreshocks are spatially clustered seismic events preceding large earthquakes. Since the dawn of seismology, their occurrence has been identified as a possible mechanism leading to further crustal destabilization, hence, to major failures. However, several cases occurred without any previous anomalous seismic activity, so that the hypothesis of foreshocks as reliable seismic precursors fails to pass statistical tests. Here, we perform an all‐round statistical comparative analysis of seismicity in Southern California to assess whether any differences can be identified between swarms and foreshocks. Our results suggest that extremely variable seismic patterns can forerun mainshocks, even though they tend to be preceded by clusters with more numerous events spread over larger areas than swarms and with a wider range of magnitudes. We provide a physical explanation of such dissimilarity and conclude, despite it, that foreshocks can hardly be reliable short‐term precursors of large earthquakes in California.
Publication Date
2024-02-05
Publisher
American Geophysical Union (AGU)
Subjects
  • Foreshocks;
  • Preparatory processes;
  • Earthquake forecasting;
  • Mainshocks;
  • 13. Climate action;
isGreen
false
isInDiamondJournal
false
Software
Publication
Name
Journal of Geophysical Research: Solid Earth
Publication
Article
iss
2
issnOnline
2169-9356
issnPrinted
2169-9313
vol
129
Other Research Product
Detailed informations
system:type
Research Product
Management Info
Author
Catalogue Manager ITINERIS
Version
1
Last Updated
May 7, 2026, 11:06 (UTC)
Created
March 24, 2026, 23:25 (UTC)
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