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.

---

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

---

Etymology

Origin of foreshock

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

Example Sentences

This may have been a foreshock - an early release of energy - but it is not a predictor of exact timing of a future earthquake, explained Prof McNeill.

From BBC • Jul. 30, 2025

Monday’s magnitude 5.2 earthquake was preceded a day earlier by a magnitude 3.3 earthquake, which is now considered a foreshock.

From Los Angeles Times • Apr. 15, 2025

Edgar provided the foreshock that inning by blasting a three-run homer in the before Luis Sojo brought home Tino Martinez on a sacrifice fly.

From Seattle Times • May 22, 2023

The inability to recognize whether an earthquake in isolation is a foreshock is a big part of why useful prediction still eludes us.

From Scientific American • Feb. 17, 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