earthquake
the vibration of Earth produced by the rapid release of energy
fault
a fracture in Earth along which movement has occurred
focus
the point within the Earth where an earthquake originates
seismic waves
vibrations that travel through Earth carrying the energy released during an earthquake
epicenter
the location on Earth's surface directly above the focus, or origin of an earthquake
elastic rebound
tendency for deformed rock along a fault to spring back to its original shape
aftershock
a small earthquake that follows the main earthquake
P-wave
earthquake wave that pushes and pulls rocks in the direction of the waves; also known as a compression wave
S-wave
a seismic wave that shakes particles perpendicular to the direction the wave is traveling (transverse wave)
seismograph
an instrument that records seismic waves
seismogram
the record made by a seismograph
surface wave
a seismic wave that travels along the surface of the Earth
moment magnitude
more precise measure of earthquake magnitude than the Richter scale, which comes from the displacement that occurs along a fault zone and estimates the energy released by an earthquake
liquefaction
a phenomenon, associated with earthquakes, in which soils and other unconsolidated materials saturated with water are turned into a liquid that is not able to support buildings
seismic gap
an area along a fault where there has not been any earthquake activity for a long period of time
tsunami
the Japanese word for a seismic sea wave
crust
the thin, rocky outer layer of Earth
mantle
the 2890 km thick layer of Earth located below the crust
lithosphere
the rigid outer layer of Earth, including the crust and upper mantle
asthenosphere
a weak plastic layer of the mantle situated below the lithosphere; The rock within this zone is easily deformed
outer core
a layer beneath the mantle about 2260 km thick; It contains liquid iron and generates Earth's magnetic field.
inner core
the solid innermost layer of Earth, about 1220 km in radius.
Moho
short for the Mohorovicic discontinuity; It is the boundary separating the crust from the mantle, discernible by an increase in the velocity of seismic waves.