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 she added that people were nervous about whether the quake "was a foreshock itself" and the "real one is on its way".

From BBC • Apr. 23, 2025

In 1970, there was a magnitude 5.2 quake with a 4.0 foreshock close to the same location, she said.

From Seattle Times • Jan. 5, 2024

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

From Scientific American • Jul. 20, 2023

Sometimes an aftershock is even larger than the initial quake, Dr. Hough said, in which case the aftershock is considered the main quake and the first one is referred to as a foreshock.

From New York Times • Feb. 6, 2023

Her early research on foreshock series — identifying certain smaller earthquakes as possible harbingers of a bigger one — enabled officials to start issuing earthquake advisories in California.

From Los Angeles Times • Mar. 30, 2016