| A | B |
|---|
| aftershock | a small earthquake that follows the main earthquake |
| asthenosphere | a weak plastic layer of the mantle situated below the lithosphere; The rock within this zone is easily deformed. |
| crust | the thin, rocky outer layer of Earth |
| earthquake | the vibration of Earth produced by the rapid release of energy |
| elastic rebound hypothesis | the explanation stating that when rocks are deformed, they break, releasing the stored energy that results in the vibrations of an earthquake |
| epicenter | the location on Earth’s surface directly above the focus, or origin, of an earthquake |
| fault | a fracture in Earth along which movement has occurred |
| focus | the point within Earth where an earthquake originates |
| foreshock | a small earthquake that often precedes a major earthquake |
| inner core | the solid innermost layer of Earth, about 1220 kilometers in radius |
| liquefaction | a phenomenon, sometimes 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 |
| lithosphere | the rigid outer layer of Earth, including the crust and upper mantle |
| mantle | the 2890-kilometer-thick layer of Earth located below the crust |
| Moho | the Mohorovi`ci` discontinuity, which is shortened to Moho; It is the boundary separating the crust from the mantle, discernible by an increase in the velocity of seismic waves |
| 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 |
| outer core | a layer beneath the mantle about 2260 kilometers thick; The outer core contains liquid iron and generates Earth’s magnetic field. |
| P wave | earthquake wave that pushes and pulls rocks in the direction of the wave; also known as a compression wave |
| S wave | a seismic wave that shakes particles perpendicular to the direction the wave is traveling |
| seismic gap | an area along a fault where there has not been any earthquake activity for a long period of time |
| seismogram | the record made by a seismograph |
| surface wave | a seismic wave that travels along the surface of Earth |
| tsunami | the Japanese word for a seismic sea wave |
