Holt Science and Technology: Inside the Restless Earth, Chapter 5, Sections 1 and 2

seismogram

a tracing of earthquake motion that is created by a seismograph

seismograph

an instrument that records vibrations in the ground and determines the location and strength of an earthquake

Richter Scale

a scale that rates an earthquakes magnitude based on the size of its seismic waves

P wave

a seismic wave that causes particles of rock to move in a back-and-forth direction

S wave

a seismic wave that causes particles of rock to move in a side-to-side direction

seismic wave

A wave of energy that travels through the Earth and away from an Earthquake in all directions.

deformation

the bending, tilting, and breaking of the earth's crust; the change in the shape of rock in response to stress

focus

the point along a fault at which the first motion of an earthquake occurs

epicenter

the point on Earth's surface directly above an earthquake's starting point, or focus

Modified Mercalli Intensity Scale

the scale is a measure of degree with which the earthquake is felt by people and the damage cause by the earthquake

seismology

the study of earthquakes

elastic rebound

the sudden return of elastically deformed rock to its original shape