Earthquakes

Aftershock

A smaller earthquake that follows a bigger one. Aftershock. An aftershock is a smaller earthquake that occurs after the main shock of a larger earthquake.

Earthquake

A sudden shaking of rock in the Earth's crust. Earthquake. An earthquake is the shaking of the ground caused by movements or shifts in the Earth's crust.

Epicenter

The point directly above the focus of an earthquake, on Earths surface. Epicenter. The epicenter is the location on the Earth's surface right above where an earthquake begins underground.

Fault

A break in Earth's crust along which rocks move. Fault. It is where Earth's plates slide past each other, causing earthquakes.

Focus

The underground point where an earthquake starts is called the focus. In simple terms, the focus is the spot beneath the Earth's surface where earthquake energy is released.

Liquefaction

The shaking during an earthquake which makes wet soil act like a liquid is called liquefaction. Liquefaction happens when the ground shakes and waterlogged soil loses its strength, causing it to flow like a liquid.

Magnitude

The strength of an earthquake. Magnitude. In Science, magnitude measures the energy released by an earthquake.

Mercalli scale

A measure of the intensity of, and damage caused by an earthquake. Mercalli scale. The Mercalli scale measures the effects and damage of an earthquake on people and buildings.

Moment magnitude scale

A scale of the energy released by an earthquake. Moment magnitude scale. The moment magnitude scale measures the size of earthquakes by calculating the energy they release.

Normal fault

A break in rock caused by tension forces, which causes rocks to slide downward. Normal fault. A normal fault occurs when tension forces in the Earth's crust pull rocks apart, causing one block to slip downward.

Primary wave

A seismic wave that vibrates rock particles in the direction that it travels. Primary wave. A primary wave, or P-wave, is a type of seismic wave that compresses and expands material in the same direction it moves, quickly traveling through Earth's crust during an earthquake.

Reverse fault

A fault caused by compression, which pushes rock upwards. Reverse fault. A reverse fault occurs when two blocks of the Earth's crust are compressed together, causing one block to move up over the other.

Richter scale

A measurement of earthquake magnitude, based on seismic wave size Richter scale. The Richter scale measures the strength of earthquakes by assessing the size of their seismic waves.

Secondary wave

A seismic wave that moves the ground up and down. Secondary wave. A secondary wave, or S-wave, is a type of seismic wave that shakes the ground perpendicular to its direction of travel, causing up-and-down or side-to-side motion.

Seismic gap

An area of few recent earthquakes, but with a history of strong quakes. Seismic gap. A seismic gap is a section of a fault that has not experienced significant earthquakes for a long time, suggesting it may be due for a future quake.

Seismic wave

An energy wave caused by an earthquake. Seismic wave. Seismic waves are vibrations that travel through the Earth, caused by the sudden release of energy during an earthquake.

Seismogram

A record of seismic waves produced by a seismograph. Seismogram. A seismogram is a visual record that shows the waves of energy moving through the Earth during an earthquake.

Seismograph

An instrument that records seismic waves. Seismograph. A seismograph is a machine that measures the shaking of the ground during an earthquake.

Stress

The force of an object pressing, pushing, or pulling on another object. Stress. Stress in Science is the measure of force applied to a material that causes it to change shape.

Strike slip fault

A break in rock where the two blocks move sideways, with little vertical movement, is called a strike slip fault. It is a type of fault where two blocks of the Earth's crust slide past each other horizontally.

Surface wave

A seismic wave that moves on a surface, it causes both up-and-down and side-to-side movement. Surface wave. In simple terms, a surface wave is a type of seismic wave that travels along the Earth's surface, causing shaking and movement.

Tsunami

A huge wave caused by an underwater earthquake. Tsunami. A tsunami is a series of large ocean waves created by the displacement of water, often due to underwater earthquakes.