earthquake

American  

[urth-kweyk] / ˈɜrθˌkweɪk /

noun

1. a series of vibrations induced in the earth's crust by the abrupt rupture and rebound of rocks in which elastic strain has been slowly accumulating.

   Synonyms:

   temblor, seism, shock, tremor, quake

2. something that is severely disruptive; upheaval.

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earthquake British  

/ ˈɜːθˌkweɪk /

noun

1. a sudden release of energy in the earth's crust or upper mantle, usually caused by movement along a fault plane or by volcanic activity and resulting in the generation of seismic waves which can be destructive

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earthquake Scientific  

/ ûrth′kwāk′ /

1. A sudden movement of the Earth's lithosphere (its crust and upper mantle). Earthquakes are caused by the release of built-up stress within rocks along geologic faults or by the movement of magma in volcanic areas. They are usually followed by aftershocks.

2. See Note at fault

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earthquake Cultural  

1. A tremor of the surface of the Earth, sometimes severe and devastating, which results from shock waves generated by the movement of rock masses deep within the Earth, particularly near boundaries of tectonic plates. (See fault, Richter scale, and seismology.)

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Closer Look

Fractures in Earth's crust, or lithosphere, where sections of rock have slipped past each other are called faults.Earthquakes are caused by the sudden release of accumulated strain along these faults, releasing energy in the form of low-frequency sound waves called seismic waves. Although thousands of earthquakes occur each year, most are too weak to be detected except by seismographs, instruments that detect and record vibrations and movements in the Earth. The point where the earthquake originates is the seismic focus, and directly above it on Earth's surface is the earthquake's epicenter. Three kinds of waves accompany earthquakes. Primary (P) waves have a push-pull type of vibration. Secondary (S) waves have a side-to-side type of vibration. Both P and S waves travel deep into Earth, reflecting off the surfaces of its various layers. S waves cannot travel through the liquid outer core. Surface (L) waves—named after the nineteenth-century British mathematician A.E.H. Love—travel along Earth's surface, causing most of the damage of an earthquake. The total amount of energy released by an earthquake is measured on the Richter scale. Each increase by 1 corresponds to a tenfold increase in strength. Earthquakes above 7 on the Richter scale are considered severe. The famous earthquake that flattened San Francisco in 1906 had a magnitude of 7.8.

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Earthquakes are particularly likely where such plates are sliding past each other, as in the San Andreas Fault.

Earthquakes cannot be accurately predicted, although the likelihood of a region's suffering an earthquake can be estimated.

Other Word Forms

• preearthquake
  adjective

Etymology

Origin of earthquake

1300–50; Middle English erthequake ( see earth, quake), replacing Old English eorthdyne ( see din ¹)

Compare meaning

How does earthquake compare to similar and commonly confused words? Explore the most common comparisons:

• earthquake vs. aftershock
• temblor vs. earthquake

Explanation

If you're visiting your friend in California and her house starts to shake, you might be experiencing an earthquake, which is the shaking of the surface of the earth that happens when there's movement deep underground. Earthquake is one of those words that means exactly what it sounds like: the earth is quaking. Earthquakes happen along "fault lines," the places where the big plates of the earth meet and rub up against each other during volcanic activities. We also use earthquake metaphorically, to talk about something that causes a violent upheaval.

Example Sentences

If so, they could function as a widespread system of natural earthquake brakes that prevents some ruptures from escalating into even larger events.

From Science Daily • May 16, 2026

In the days and weeks before a major earthquake, the barrier zones experienced bursts of small seismic activity.

From Science Daily • May 16, 2026

"We have our earthquake machine... Now we have to play with the parameters," said Frederic Massin, a French seismologist and technical expert, as he studied his screen for clues to what had caused the outage.

From Barron's • May 11, 2026

The most intense earthquake reached a magnitude of 4.7 shortly after midnight in the early morning Sunday, according to the United States Geological Survey.

From Los Angeles Times • May 10, 2026

It may seem ruthless, but the strategy is simple: When a strong earthquake strikes, a tsunami is likely following close behind.

From "Meltdown" by Deirdre Langeland

Related Words

• shock
• temblor
• upheaval