Chapter 9 Vocabulary
| Word | Definition |
|---|---|
| body wave | A seismic wave that travels through Earth's interior. |
| earthquake | 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 | Gradual displacement along a fault. Such activity occurs relatively smoothly and with little noticeable seismic activity. |
| focus | The zone within Earth where rock displacement produces an Earthquake. |
| foreshocks | Small earthquakes that often precede a major earthquake. |
| liquefaction | The process by which unconsolidated material fills with water, making the soil unstable. Earthquake vibrations can force these water-filled sediments to flow, leading to structural failure. |
| magnitude | The total amount of energy released during an earthquake. |
| megathrust fault | The plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate. |
| modified Mercalli intensity scale | A 12-point scale developed to evaluate earthquake intensity based on the amount of damage to various structures. |
| Mohorovičić discontinuity | The boundary separating the crust and the mantle, discernible by an increase in seismic velocity. |
| moment magnitude | A more precise measure of earthquake magnitude that is derived from the amount of displacement that occurs along a fault zone. |
| P wave | The fastest earthquake wave; it travels by compression and expansion of the medium. |
| paleoseismology | The study of the timing, location, and size of prehistoric earthquakes. |
| Richter scale | A scale of earthquake magnitude based on the motion of a seismograph. |
| S wave | A seismic wave that involves oscillation perpendicular to the direction of propagation. |
| seismogram | The record made by a seimograph. |
| seismograph | An instrument that records earthquake waves. |
| seismology | The study of earthquakes and seismic waves. |
| shadow zone | The zone between 105 and 140 degrees distance from an earthquake epicenter that direct waves do not penetrate because of refraction by Earth's core. |
| surface wave | A seismic wave that travels along the outer layer of Earth. |
| tsunami | A rapidly moving ocean wave generated by earthquake activity and capable of inflicting heavy damage in coastal regions. |