Earthquakes Glossary

The series of smaller earthquakes that follow a major earthquake.

The instant at which an earthquake wave appears at a seismograph station.

Seismic waves that pass through the interior of the Earth.

Waves in which particles of material move back and forth parallel to the direction in which the wave itself moves.

The amount of movement or slip across a fault plane.

A vibration caused by the sudden breaking or frictional sliding of rock in the Earth.

The design of buildings that can withstand shaking.

The determination of where land is relatively stable and where it might collapse because of seismicity.

An explanation for how energy is spread during an earthquake. As plates on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded. At that time, a sudden movement occurs along the fault, releasing the accumulated energy, and the rocks snap back to their original undeformed shape.

The point on the surface of the Earth directly above the focus of an Earthquake.

A fracture on which one body of rock slides past another.

Gradual movement along a fault that occurs in the absence of an earthquake.

A small step on the ground surface where one side of a fault has moved vertically with respect to the other.

The intersection between a fault and the ground surface.

The location where a fault slips during an earthquake.

The series of smaller earthquakes that precede a major earthquake.

Seismic events caused by the actions of people (e.g. filling a reservoir that lies over a fault with water).

Earthquakes that occur away from plate boundaries.

Surface seismic waves that cause the ground to ripple back and forth, creating a snake-like movement.

The abrupt loss of strength of a wet sediment (either sand or clay) in response to ground shaking.

An earthquake characterisation scale based on the amount of damage that the earthquake causes.

A number that indicates the relative size of an earthquake, as determined by measuring the maximum amplitude of ground motion recorded by a seismograph.

Compressional seismic waves that move through the body of the Earth.

Surface seismic waves that cause the ground to ripple up and down, like water waves in a pond.

The average time between successive geologic events.

This occurs when each new wave arrives at just the right time to add more energy to a system.

A scale that defines earthquakes on the basis of the amplitude of the largest ground motion recorded on a seismogram.

Seismic shear waves that pass through the body of the Earth.

Rhythmic movement in a body of water caused by ground motion.

The relatively narrow strips of crust on Earth under which most earthquakes occur.

A potentially dangerous area where a known active fault has not slipped for a long time.

Waves of energy emitted at the focus of an earthquake.

The record of an earthquake produced by a seismograph.

An instrument that can record the ground motion from an earthquake.

Seismic waves in which particles of material move back and forth perpendicular to the direction in which the wave itself moves.

Stop-start movement along a fault plane caused by friction, which prevents movement until stress builds up sufficiently.

Seismic waves that travel along the Earth's surface.

A graph that plots the time since an earthquake began on the vertical axis, and the distance to the epicentre on the horizontal axis.

A large wave along the sea surface triggered by an earthquake or large submarine slump.

A sloping band of seismicity defined by intermediate and deep-focus earthquakes that occur in the downgoing slab of a convergent plate boundary.