foreshock

American  

[fawr-shok, fohr-] / ˈfɔrˌʃɒk, ˈfoʊr- /

noun

Geology.

1. a relatively small earthquake that precedes a greater one by a few days or weeks and originates at or near the focus of the larger earthquake.

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foreshock British  

/ ˈfɔːˌʃɒk /

noun

1. a relatively small earthquake heralding the arrival of a much larger one. Some large earthquakes are preceded by a series of foreshocks Compare aftershock

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Etymology

Origin of foreshock

First recorded in 1900–05; fore- + shock ¹

Example Sentences

But conventionally, only half of earthquakes have an easily detectable foreshock, while the other half do not.

From Los Angeles Times • Dec. 22, 2025

However, the 2011 earthquake was preceded by a 7.2 magnitude foreshock, they note - one which was largely ignored.

From BBC • Aug. 9, 2024

It’s not clear that a quake is a foreshock until a larger quake happens.

From Scientific American • Jul. 20, 2023

The downfall of the Fox host Bill O'Reilly in April 2017 turned out to have been just a foreshock of the changes to come.

From New York Times • Oct. 23, 2018

The foreshock was the abrupt shuttering, save for a skeleton-crew website still bearing the nameplate, of the venerable, Hearst-owned Post-Intelligencer.

From Seattle Times • Mar. 8, 2018