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Foreshocks. Smaller earthquakes preceding a large earthquake (the mainshock) in an earthquake sequence.
Earthquakes typically occur in sequences that may include foreshocks, the mainshock (the largest event or events), and aftershock (“Earthquake, Aftershocks”). Earthquake sequences without a clear mainshock are called swarms.
Foreshocks are the most obvious premonitory phenomenon of earthquakes. They are thought to indicate earthquake nucleation and hence may have the potential for short-term earthquake prediction (Scholz 2002). However, proof of the physical link between foreshocks and earthquake nucleation is inconclusive, and earthquake prediction using foreshocks has not been reliable.
The problem begins with their recognition – foreshocks are earthquakes that are called foreshocks retrospectively, when a large event (the mainshock) followed. To be considered as foreshocks, these events need to occur within certain spatial and temporal...
- Helmstetter A, Sornette D, Grasso J-R (2003) Mainshocks are aftershocks of conditional foreshocks: how do foreshock statistical properties emerge from aftershock laws. J Geophys Res 108:2046Google Scholar
- Jones LM (1985) Foreshocks and time-dependent earthquake hazard assessment in southern California. Bullet Seismolog Soci Am 75:1667–1679Google Scholar