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

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.

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.

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).

View a collection of sound animations, which depict how a source of sound waves pushes against particles to carry energy away without matter being displaced.

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.

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.

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

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.

Tectonic earthquakes are caused by tectonic plates sliding past one another at fault zones, deforming rock through friction as energy builds like a stretched rubber band.

Convection flows in Earth’s mantle drive the movement of tectonic plates

These processes transfer heat from Earth’s core to the surface via rising magma plumes, while cooler, denser rock falls into the mantle at rates similar to human fingernail growth. These rates are determined by combining seismic data with computer simulations to model Earth’s interior.

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.

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

Explore a visual and auditory guide to wave properties and waveforms to learn how every sound imaginable can be created by combining multiple vibrations of air.

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.

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.

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

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.

A tsunami—Japanese for 'harbor wave'—can begin with a drop in sea level before rising, which has contributed to its mistaken categorization as a tidal wave, despite being unrelated to the moon's gravity.

Tsunamis are a series of waves rather than a single one, and boats are safer from them in deeper waters, where tsunami waves are smaller.

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...

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.

Heat slowly moves through Earth's mantle like softened wax

Energy trapped during Earth's formation and released via the radioactivity of elements is carried by convection currents towards the surface, while cooler, denser material sinks. The planet's core is almost as hot as the sun's surface.

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.

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.

View the electromagnetic spectrum and the properties of different types of light

All forms of electromagnetic radiation, from radio waves to gamma rays, travel at the speed of light in a vacuum, but their wavelengths decrease as their frequencies increase. The light-sensitive nerve cells in the human eye are sensitive to a narrow range of values, which we observe as the spectrum of visible light.

Cosmic rays are thought to be accelerated to near the speed of light by repeatedly bouncing across shockwaves produced by high-energy cosmic events, such as supernovae.

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.

In 1974, a pair of neutron stars provided the first evidence of gravitational waves

Observations of a pulsar—a rapidly rotating neutron star that emits light—revealed it to be part of a system of two stars that orbited one another in a shrinking orbit, indicating gradual energy loss. Calculations showed that the changing orbit was consistent with gravitational waves predicted to carry energy away from such a system.

Objects that move faster than the speed of sound—Mach 1—create shockwaves called sonic booms by building up and forcing sound waves to combine as they lag behind the object.

Probability waves govern particles like electrons in the quantum space

Just as waves are extended objects whose heights change across space, quantum waves dictate that the probability of an object existing in different locations across space varies. Like water waves, the probability waves can combine, changing the heights—and therefore probabilities—in different locations.

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.

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.

Listen to the pair of colliding black holes detected by LIGO

As ripples in spacetime, gravitational waves do not produce sound, which is the perception of specific vibrations in matter (e.g., vocal cords vibrating air molecules). The "chirp" of gravitational waves comes instead from converting the spacetime ripples into sound waves that the human ear can hear.

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.

Wind is the movement of air caused by the sun's uneven heating of Earth

The tilt, curvature, and variations in Earth's surface composition across the globe cause different regions to receive different amounts of solar radiation. As the Earth spins and tries to achieve thermal equilibrium, air masses move and interact, creating wind.

Wind energy is categorized into land-based, distributed, and offshore types

Distributed wind turbines efficiently serve on-site energy needs, while land-based turbines are large and generate cost-competitive electricity. Offshore wind turbines capture powerful winds above the ocean and may be pounded into the seafloor using pile drivers or built to float above water at scales larger than the Statue of Liberty.

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.

Some tectonic plates move faster than their underlying convection currents

Like a chain slipping off a ledge, as tectonic plates sink, their weight can pull the rest of the trailing plate forward, accelerating their movement. Plates can also break apart and fall, creating a suction effect that drives movement, resembling leaves following a passing car.

Earth’s major tectonic plates make up 95% of its surface

Tectonic plates are pieces of Earth’s lithosphere, which consists of the crust and the solid, upper layer of the mantle. Segments of major plates can break and form minor or microplates, whose total number varies based on ongoing geological activity.

Interacting sound waves can create regions where the pressure from each wave combines, allowing objects to levitate in place against gravity or be manipulated for touch-free construction.

When struck, objects vibrate at unique rates called resonant frequencies, which makes tapping wood sound different from tapping metal, but providing objects with sound at their resonant frequency can cause them to shatter.

Radio waves are used in broadcasting, weather radar, telecommunications, and GPS

Its ability to bend around obstacles and reflect off the ionosphere—an electrified layer of Earth's upper atmosphere—allows this type of light to travel long distances without damaging living things due to its low energy. MRI scanners, WiFi, and Bluetooth technologies are also applications of this form of light.

The continuous decay of radioactive elements regenerates geothermal energy reserves

Geothermal power is a renewable energy source derived from Earth's interior, where the core reaches temperatures exceeding 5,000 degrees Celsius (9,000 degrees Fahrenheit). These temperatures result from leftover energy from collisions during planetary formation, with radioactive decay in the core releasing additional energy that travels to the surface.

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.

Geothermal power can generate electricity and provide direct heating for homes

By drilling several kilometers through penetrable rock, wells can access highly pressurized groundwater warmed by thermal energy trapped beneath Earth's surface. This water can be turned into steam to create electricity in generators. Heating systems several meters deep can pump fluid underground before circulating it through buildings.

Earth's inner structure is a dynamic system of layers in constant, slow motion

From the crust to the core, each of Earth's layers—some solid, some liquid—plays a role in generating its magnetic field, moving tectonic plates, and cycling matter. These details are determined through modeling since humans have only drilled 12 kilometers underground.

Ultrasound machines emit and receive high-frequency sound waves to construct images of the body's interior, with differences in the penetrating power of different frequencies allowing medical professionals to identify different structures.

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

The Ring of Fire, which spans 40,000 kilometers (24,900 miles) around the Pacific Ocean, is the most geologically active region on Earth.

Thunder occurs when fast-flowing electricity heats and pressurizes air, causing it to expand and produce a shockwave at each point along the bolt at multiple frequencies.