Chapter 8: Earthquakes and Earth's Interior

earthquake

the vibration of Earth produced by the rapid release of energy within the lithosphere

fault

fractures in Earth where movement has occurred

focus

the point within Earth where an earthquake starts

seismic waves

vibrations that travel through Earth carrying the energy released during an earthquake

epicenter

the location on the surface directly above the focus of an earthquake

uplifted crust

crust that has been moved up vertically by an earthquake

fault scarp

sharp-edged ridge formed by vertical crust movement

offset crust

displaced; crust that has been moved horizontally by an earthquake

elastic rebound hypothesis

most earthquakes are produced by the rapid release of energy stored in rock that has been subjected to great forces and when the the strength of the rock has been exceeded, it suddenly breaks, releasing some of its stored energy as seismic waves

elastic rebound

the tendency for deformed rock along a fault to spring back after an earthquake

aftershock

an earthquake that occurs hours or even weeks after a major earthquake

foreshock

small earthquake that occurs sometime before a major earthquake

body waves

seismic waves that travel through Earth's interior

P waves

compressional waves; seismic waves that push and pull particles in the direction the waves travel

S waves

transverse waves; shake particles at right angles to the wave's direction of travel

surface waves

seismic waves that travel along the surface of Earth

seismograph

an instrument that records seismic waves

seismogram

the record made by a seismograph

intensity

a measure of the amount of earthquake shaking at a given location based on the amount of damage

magnitude

a measure of the size of seismic waves or the amount of energy released at the source of the earthquake

moment magnitude

a more precise measure of earthquake magnitude than the Richter scale, which is derived from the amount of displacement that occurs along a fault zone and estimates the energy released by an earthquake

Modified Mercalli scale

scale the rates earthquakes' intensity in terms of the earthquakes' effects at different locations