| A | B |
|---|
| aftershock | Smaller earthquakes that follow the main earthquake. |
| asthenosphere | A subdivision of the mantle situated below the lithosphere. |
| body wave | Seismic waves that travel through Earth's interior. |
| crust | The very thin outermost layer of Earth. |
| earthquake | The vibration of Earth produced by the rapid release of energy. |
| elastic rebound | The sudden release of stored strain in rocks that results in movement along a fault |
| epicenter | The location on Earth's surface that lies directly above the focus of an earthquake. |
| fault | A break in a rock mass along which movement has occurred. |
| fault creep | Displacement along a fault that is so slow and gradual that little seismic activity |
| focus | The zone within Earth where rock displacement produces an earthquake. |
| foreshock | Small earthquake that often precede a major earthquake. |
| inner core | The solid innermost layer of Earth, about 1300 kilometers (800 miles) in radius. |
| liquefaction | A phenomenon in which soils and other unconsolidated materials containing abundant water are turned into a fluidlike mass |
| lithosphere | The rigid outer layer of the earth, including the crust and upper mantle |
| magnitude | The total amount of energy released during an earthquake. |
| mantle | The 2900-kilometer (1800- mile)-thick layer of Earth located below the crust. |
| Mercalli intensity scale | A 12-point scale originally developed to evaluate earthquake intensity based on the amount of damage to various Structures. |
| Mohorovicic discontinuity (Moho) | The boundary separating the crust from the mantle, discernible by an increase in seismic velocity. |
| outer core | A layer beneath the mantle about 2200 kilometers (1364 miles) thick that has the properties of a liquid. |
| primary (P) wave | A type of seismic wave that involves alternating compression and expansion of the material through which it passes. |
| Richter scale | A scale of earthquake magnitude based on the motion of a seismograph. |
| secondary [S] wave | A seismic wave that involves oscillation perpendicular to the direction of propagation |
| seismic sea wave | A rapidly moving ocean wave generated by earthquake activity capable of inflicting heavy damage in coastal regions. |
| seismogram | The record made by a seismograph. |
| seismograph | An instrument that records earthquake waves. |
| seismology | The study of earthquakes and seismic waves |
| shadow zone | The zone in which direct waves do not arrive because of refraction by Earth's core. |
| surface wave | Seismic waves that travel along the outer layer of Earth. |
| Tsunami | The Japanese word for a seismic sea wave |
