Chapter 12 Vocabulary

earthquake

a movement or trembling of the ground that is caused by a sudden release of energy when rocks along a fault move

elastic rebound

the sudden return of elastically deformed rock to its undeformed shape

focus

the location within earth along a fault at which the first motion of an earthquake occurs

epicenter

the point of earth's surface directly above an earthquake’s starting point, or focus

body wave

a seismic wave that travels through the body of a medium

surface wave

a seismic wave that travels along the surface of a medium and that has a stronger effect near the surface of the medium than it has in the interior

p wave

a primary wave, or compression wave; a seismic wave that causes particles of rock to move in a back-and-forth direction parallel to the direction in which the wave is traveling

s wave

a secondary wave, or shear wave; a seismic wave that causes particles of rock to move in a side-to-side direction perpendicular to the direction in which the wave is traveling

shadow zones

an area of earth’s surface where no direct seismic waves from a particular earthquake can be detected

fault zones

a region of numerous, closely spaced faults

seismograph

an instrument that records vibrations in the ground

seismogram

a tracing of earthquake motion that is recorded by a seismograph

magnitude

a measure of the strength of an earthquake

tsunami

a giant ocean wave that forms after a volcanic eruption, submarine earthquake, or landslide

seismic gap

an area along a fault where relatively few earthquakes have occurred recently but where strong earthquakes are known to have occured in the past