| A | B |
|---|
| Fault | A fracture in Earth’s crust where the rocks on either side have moved |
| Earthquake | The shaking and vibration caused by plate movement and rocks breaking along a fault |
| Normal fault | A break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below the fault surface |
| Reverse fault | A break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below the fault surface |
| Strike-slip fault | A break in rock caused by shear forces, where rocks move past each other without much vertical movement |
| Seismic wave | Any wave generated by an earthquake |
| Focus | In an earthquake, the point below Earth’s surface where energy is released in the form of seismic waves |
| Epicenter | The point on Earth’s surface directly above an earthquake’s focus |
| Primary wave | A seismic wave that moves rock particles back and forth in the same direction that the wave travels |
| Secondary wave | A seismic wave that moves rock particles at right angles to the direction of the wave |
| Surface wave | A seismic wave that moves rock particles up and down in a backward rolling motion and side to side in a swaying motion |
| Seismograph | The instrument used to register earthquake waves and record the time that each arrived |
| Magnitude | The measure of the energy released during an earthquake |
| Liquefaction | A process that occurs when wet soil acts more like a liquid during an earthquake |
| Tsunami | A seismic sea wave that begins over an earthquake focus and can be highly destructive when it crashes on shore |
