phenomenon

earthquake

A sudden slip on a fault caused by accumulated stress, releasing seismic energy.
17 related articles

Description

An earthquake is a sudden, rapid shaking of the ground caused by the release of accumulated stress along a geological fault. Over time, tectonic forces slowly deform the rocks on either side of a fault, storing elastic energy like a stretched spring. When the stress exceeds the frictional strength of the fault, the rocks slip abruptly, converting the stored energy into seismic waves that radiate outward and shake the surface.

History

The modern understanding of earthquakes as elastic rebound was developed by Harry Fielding Reid in 1910, following the 1906 San Francisco earthquake. He proposed that accumulated elastic strain is suddenly released when the fault slips.

How it works

The process begins with slow tectonic loading that builds stress across a fault. The fault's surfaces are held together by friction, which resists sliding. As stress increases, the fault may initially creep or stick in a series of small events. Eventually, the shear stress overcomes the static friction, causing a sudden rupture. The rupture propagates along the fault at kilometers per second, releasing energy as seismic waves. The behavior of the fault—whether it slips smoothly or in a stick-slip manner—depends on the frictional properties of the materials and the presence of fluids or gouge (crushed rock) in the fault zone.

In practice

Seismic hazard assessment and building design codes use earthquake mechanics to estimate ground shaking and design structures that can withstand it. Understanding fault friction also helps in interpreting induced seismicity from activities like wastewater injection.

Fun fact

The friction in a fault can be so sensitive that a tiny change in stress—equivalent to the weight of a coin—can trigger a large earthquake if the fault is already near its critical state.

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Related articles · 17

Geophysics2026-08-171 minarXiv:2608.16317express
Earthquake Swarm: How Granite Comes Alive
In 2019, residents of Palghar district in western India felt the ground slip from under their feet — not once, but thousands of times. Over two years, seismographs recorded about 50,000 tremors. This wasn't a typical earthquake with a main shock and aftershocks, but a swarm: a series of events that quiets down and then flares up again, like a smoldering fire fed with twigs.
Geophysics2026-07-262 minarXiv:2607.23736express
Why the Fault Decides Whether an Earthquake Happens
Two pieces of sandpaper are pressed tightly together. As you start to slide them, they first catch on the rough spots, then suddenly slip. A fault in the Earth behaves much the same way during an earthquake. But there's a crucial detail: how far do you need to push the edges before the grip gives way? This distance is called the critical slip distance.
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Geophysics2026-03-291 minarXiv:2603.27860express
How to Hear the Earth's Crust Cracking in Advance
Seismologists catch every underground tremor the way a doctor listens to a heart. But small earthquakes have weak and fuzzy signals: it's hard to tell exactly where the rock shifted. Usually, scientists look at the first wave motions: compression or dilation. But if the tremor starts gently, without a sharp snap, the picture gets blurred.
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Fluid Dynamics2026-03-151 minarXiv:2603.14237express
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Plasma Physics2026-02-241 minarXiv:2602.21422express
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Materials2026-02-121 minarXiv:2602.12427express
Friction in Faults: How Sand Turns into an Earthquake
When two tectonic plates grind against each other, a layer of pulverized rock ends up between them, like sand between your palms. This layer, which geologists call fault gouge, behaves not like solid rock but like a thick paste: it can compact, dilate, and slide. Whether a fault ruptures in a devastating earthquake or creeps slowly and safely depends on its whims.
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A thin rubber film lies on a table. Someone grabs it by the middle and slowly pulls upward. The film doesn't just rise: it arches into a dome, then wrinkles run along the dome's edge, like pleats on a skirt. Pull higher — the wrinkles gather into large folds that cross the entire film. And if you start lowering it, the folds don't disappear but collapse into new shapes.
Fluid Dynamics2025-11-071 minarXiv:2511.05351express
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When liquid is swirled in a cup, a vortex with an empty center forms. In this empty core, waves find a trap: bouncing off the walls, they siphon energy from the vortex and grow like a flame along a fuse — each wave stronger than the last, until a surge breaks loose. Astrophysicists have described the same chain reaction around black holes.
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