| A | B |
|---|
| seismology | the study of earthquakes |
| fault | a break in the Earth's crust along which blocks of the crust slide relative to one another due to tectonic forces |
| deformation | the change in the shape of rock in response to stress |
| elastic rebound | the sudden return of elastically deformed rock to its undeformed shape. |
| seismic waves | waves of energy that travel through the Earth |
| P waves | the fastest type of seismic wave; can travel through solids, liquids, and gases; also known as pressure waves and primary waves |
| S waves | the second-fastest type of seismic wave; cannot travel through materials that are completely liquid; also known as shear waves and secondary waves |
| seismograph | an instrument located at or near the surface of the Earth that records seismic waves |
| seismogram | a tracing of earthquake motion created by a seismograph |
| epicenter | the point on the Earth's surface directly above an earthquake's starting point |
| focus | the point inside the Earth where an earthquake begins |
| gap hypothesis | states that sections of active faults that have had relatively few earthquakes are likely to be the sites of strong earthquakes in the future |
| seismic gap | an area along a fault where relatively few earthquakes have occurred |
| Moho | a place within the Earth where the speed of seismic waves increases sharply; marks the boundary between the Earth's crust and mantle |
| shadow zone | an area on the Earth's surface where no direct seismic waves from a particular earthquake can be detected |
