Scientists determine earthquake locations by comparing how long it takes different seismic waves to be detected at three stations around the world, from which an origin, or hypocenter, can be triangulated.

Just as light bends at different angles as it travels through different materials, seismic waves move in different directions through Earth's interior, revealing the presence of layers with varying properties.

Rather than predicting them in advance, earthquake early warning systems detect tremors moments after they begin and send notifications that reach users before the seismic activity does.

Because seismic waves travel 100 times faster than tsunami waves—waves typically travel faster through solids than liquids—measurements of geological activity help tsunami detection systems provide early warnings.

Thunderquakes—seismic waves created when lightning strikes the ground—have enabled scientists to image underground environments near Earth's surface by detecting vibrations along subterranean fiber-optic cables.

Scientists investigate Earth's interior by studying seismic waves

Scientists investigate Earth's interior by studying seismic wavesBelow Earth's atmosphere lies the crust, which extends to the Mohorovičić discontinuity between five and 20 miles below Earth's surface. Below the crust lies the mantle, the liquid-metal outer core, and the solid inner core, which surpasses 5,200 degrees Celsius (9,392 degrees Fahrenheit).

The frequency of earthquakes and the distribution of their magnitudes have not changed significantly over long-term records, but technological improvements have enabled scientists to detect more of them as they occur.

View maps of seafloor topography, earthquakes, and volcanic activity, which scientists use to create outlines of Earth's tectonic plates.

Some earthquakes can produce smaller tremors called boomerang earthquakes, which travel in the opposite direction and ripple back to the original earthquake's source.

Potential LIGO sites were selected in pairs, approximately 3,000 kilometers apart

The 1,864-mile distance meant gravitational wave signals would be detected no more than 10 milliseconds apart, ruling out many background signals. The sites needed sufficient plots of nearly flat land, proximity to infrastructure (e.g., electricity), and adequate distance from urban areas and geologically active areas to reduce environmental noise.

The four types of seismic waves—vibrations that carry energy generated by geological events, such as earthquakes—are categorized as body or surface waves.

Since 2017, Virgo has helped LIGO localize astronomical phenomena

The detector near Pisa, Italy, coordinates its experimental runs with those in Hanford, Washington, and Livingston, Louisiana. Scientists can triangulate the locations of celestial events that generate gravitational waves using signal arrival times, just as earthquake locations can be determined from measurements at three seismic stations.

View a tsunami travel time map to learn how many hours its waves are estimated to take to reach different parts of Earth when originating from a list of geologically active locations.

Scientists determined that tectonic plates moved the ocean floor by observing symmetric patterns of magnetic stripes on opposite sides of underwater volcano systems, which could only result from seafloor spreading.

What makes the Earth shake?

Researchers are demystifying the science of earthquakes—from their origins deep within the Earth to the scales that measure their strength. This article, which was part of a series of weekly reports from Cornell University, serves as a guide to...

Reported earthquake magnitudes often change because initial values are based on limited information, whereas revised magnitudes account for factors such as fault size, rupture duration, and seismic wave behavior.

View the past month of earthquakes worldwide with this digital globe, which displays data from the US Geological Survey.

Earthquakes of identical magnitudes are unlikely to cause equal damage because magnitude only measures energy released, and earthquake severity depends on environmental factors, such as local architecture and geological conditions.

Scientists can map Earth's shape and structure by measuring the ratios of certain particles arriving from different directions in space, as these ratios change with the density of the material particles travel through.

Because the Richter scale was calibrated to crustal and mantle properties in Southern California, seismologists have instead used the moment magnitude scale to quantify earthquakes since the 1970s.

View a map of the world's major earthquakes from 1956 to 2022, which can be used to identify tectonic plate boundaries.

Although earthquakes cause about 80% of tsunamis, almost all earthquakes lack sufficient energy to cause the sudden shift in the ocean floor needed to substantially displace enormous volumes of water.

NASA's GUARDIAN software uses changes in satellite navigation signals and AI-powered detection algorithms to anticipate tsunamis and provide real-time alerts to at-risk communities before the phenomena are detected by tidal sensors.

Predicting earthquakes is difficult because different rock types can withstand different amounts of stress before breaking and melt at different temperatures within Earth's interior, introducing uncertainty into predictive models.

The next generation of gravitational wave detectors may include a triangular design

The Einstein Telescope will use three pairs of underground detectors—each with arms separated by 60 degrees—arranged in an equilateral triangle. The European observatory will work alongside the Cosmic Explorer, a pair of new US detectors, to provide an eightfold increase in sensitivity over LIGO and extend the current detection frequency range.

Gravitational waves—ripples in the fabric of spacetime—are detected at LIGO by measuring how two lasers traveling down equally distant, perpendicular tunnels interfere with one another after they reflect back and meet.

Track lightning strikes around the world

The Blitzortung platform triangulates the positions of this phenomenon from stations that detect atmospheric interference in low-frequency signals that are characteristic of lightning strikes. A network of nearly 2,000 stations transmits the required data to a central server, where its software performs these calculations and generates the subsequent visualization.

The history of helioseismology, which studies seismic waves traveling within the sun

Following World War II, scientists began studying the sun's influence on radio waves, the most popular form of mass communication at the time. NASA missions to study the sun's interior have since helped develop explanations for various phenomena in its atmosphere and protect digital infrastructure.

Why starquakes may explain various phenomena associated with neutron stars

Fast radio bursts—repeated millisecond-long pulses of enormous energy from neutron stars—are emitted with a timing that resembles the earthquakes and aftershocks seen on Earth when geological activity releases energy from within the planet. Although pulsars should gradually spin more slowly as they lose energy from emitting jets of radiation, sudden increases may result from interior matter moving during starquakes.

The earliest earthquake-detection device—the seismoscope—was invented in China in 132 CE and featured eight ball-wielding dragons facing different directions.

Scientists define sea level as the elevation to which water would settle on Earth's surface, given the planet's gravitational field and rotation.

When GPS and sonar are unavailable, submarine navigation relies on a fiber-optic gyroscope to determine the vessel's orientation and an accelerometer to calculate distance traveled.

Likened to a car backfiring or a faraway cannon fire, skyquakes have been reported worldwide in Earth's atmosphere without any obvious cause.

The world's largest earthquake simulator is an 800-ton shake table facility in Miki, Japan, which was built to test the resilience of structures after the 1995 Kobe earthquake killed over 6,000 people.

Visualize the power and frequency of earthquakes across the moment magnitude scale, where a whole number increase corresponds to about 32 times more energy released.

GPS satellites are programmed to account for their faster passage of time in space

The Global Positioning System relies on signals from satellites to calculate locations on Earth by measuring time and distance. However, their orbits, being farther from Earth's center, cause them to experience less gravitational time dilation. These systems would be off by 11 kilometers per day without relativistic corrections.

Rather than being triggered by a massive displacement of water from a geological event, meteotsunamis are caused by rapid changes in air pressure from fast-moving weather systems.

Gravitational waves—ripples in spacetime that result from the motion of objects—were detected a century after Albert Einstein predicted their existence upon developing his theory of gravity.

Records of Earth's magnetic field on the seafloor validated plate tectonics

Matching glacial, fossil, and rock records, mountain ranges, and continental shapes across oceans was insufficient evidence for continental drift. Precise measurements of magnetic minerals on the ocean floor revealed seafloor spreading, which could only be explained by moving landmasses.

Particle accelerators detect subatomic particles using millions of sensors

Calorimeters measure the energy of particles. Tracking devices can measure momentum and charge from the trajectory of particles, which is determined by recording tiny electrical signals. Time-of-flight detectors provide particle velocities directly and particle mass indirectly, giving physicists a suite of properties to compare with those of known matter.

Explore an interactive time-lapse of reported tsunami events since 1850, with identified cause, recorded observations, known deaths, and other information available for each.

Explaining why the Earth wobbles

Astronomers going back to Hipparchus in the 2nd century BCE have noticed our planet has a distinct wobble. More recently, scientists have observed that the Earth is 26 miles wider at the equator than from pole to pole. The wobble results from our...

Enhanced geothermal power systems can trigger earthquakes by injecting fluid into rock, increasing subterranean pressure.

LIGO made the first detection of gravitational waves

On February 11, 2016, scientists at the Laser Interferometer Gravitational-Wave Observatory announced the confirmed detection of ripples in spacetime, which were produced from the collision of two black holes 36 and 29 times the mass of the sun. The detection confirmed that gravitational waves travel at the speed of light, as predicted by Albert Einstein in 1915.

As of 2025, humans have only dug 0.2% the way to Earth's center

The Kola Superdeep Borehole revealed two billion-year-old fossils and underground water, but the immense temperature and pressure prevented further tunneling. Beyond those depths, scientists know of Earth's interior by analyzing how seismic waves move.

How we know what's deep inside the Earth, despite never traveling there

We'll likely never see the Earth's core, but we can make educated guesses about what it's like down there. Nearly as hot as the sun's surface and under impossibly high pressure, the inner Earths extreme conditions make it impossible to explore. Yet, seismic waves during earthquakes, volcanic eruptions, and light waves from the sun provide fascinating insights about our planet's mantle, crust, and core.

Sonar, or sound navigation and ranging, uses reflected sound waves to map and detect seafloor features, marine organisms, and other obstacles.

Why the ratios of helium isotopes are analyzed to investigate ocean circulation

Volcanic activity on the seafloor produces high ratios of helium-3 to helium-4, which can be tracked in ocean samples more easily than other elements because helium is nonreactive. Water from deep ocean currents can also be distinguished from air-exposed surface water sources by comparing these ratios, since atmospheric helium ratios are much lower.

Delays in the decay of unstable particles provide evidence for time dilation

Physicists used the muon half-life measured in labs to predict how many should reach detectors on Earth's surface after their production in collisions between atmospheric molecules and cosmic rays. Higher detection rates were consistent with a longer half-life due to slower movement through time.

Micro-seismic activity has been produced from people cheering or dancing at sporting events, concerts, and other large gatherings, but scientists can easily distinguish these vibrations from natural earthquakes using seismometers.

Wave tanks can be used to create and study the impacts of tsunamis by building tension in an underwater object before allowing it to slip and rapidly displace water.