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Related to foreshock: tsunami, aftershock


A minor tremor of the earth that precedes a larger earthquake originating at approximately the same location.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Geological Science) a relatively small earthquake heralding the arrival of a much larger one. Some large earthquakes are preceded by a series of foreshocks. Compare aftershock
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈfɔrˌʃɒk, ˈfoʊr-)

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.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.foreshock - a tremor preceding an earthquake
earth tremor, microseism, tremor - a small earthquake
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
* Two of strongest earthquakes to strike Southern California since 1999 occurred during the first week of July: a magnitude-6.4 foreshock on July 4 and a magnitude-7.1 mainshock on July 5.
"Many of these foreshock earthquakes are small in magnitude and hence were previously undetected by the seismic network."
Usually, an earthquake consists of a foreshock, earthquake, and aftershocks.
At 7.1 it was an aftershock, 11 times stronger than the 6.4 foreshock that struck the day before.
The question terrorizing nervous Californians is if the magnitude 7.1 quake that hit Ridgecrest on July 5 was the "main event," or was it just the foreshock to a more devastating quake seismologists believe has a two percent chance of devastating California over the next few weeks?
The July 4, 2019 6.4 magnitude earthquake that struck Searles Valley, California, proved to be a foreshock for a larger 7.1 magnitude earthquake that struck near Ridgecrest, California on July 5, 2019.
When an aftershock is bigger than the main quake, the first quake is renamed as a foreshock, Jones explained.
A powerful magnitude 7.1 earthquake shook Southern California on Friday, causing some damage to buildings, with 11 times more force than an apparent foreshock that rattled the same area a day earlier.
However, that quake would now be considered a foreshock to the Friday night temblor.
4 is now a foreshock, and that 7.1 aftershock has become the main shock.
4-magnitude quake "foreshock" the previous day, according to the United States Geological Survey.