| A | B |
|---|
| 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 |
