| A | B |
|---|
| epicenter | The point on Earth's SURFACE directly ABOVE an earthquake's focus. |
| focus | The point BENEATH Earth's surface where rock breaks under stress and causes an earthquake. |
| magnitude | The measurement of an earthquake's strength based on seismic waves and movement along faults. |
| Mercalli scale | A scale that rates earthquakes according to their intensity and how much damage they cause. |
| moment magnitude scale | A scale that rates earthquakes by estimating the total energy released by an earthquake. |
| P wave | A type of seismic wave that compresses and expands the ground. |
| Richter scale | A scale that rates seismic waves as measured by a particular type of mechanical seismograph. |
| S wave | A type of seismic wave that moves the ground up and down or side to side. |
| seismic wave | A vibration that travels through Earth carrying the energy released during an earthquake. |
| seismograph | A device that records ground movements caused by seismic waves as they move through Earth. |
| surface wave | A type of seismic wave that forms when P waves and S waves reach Earth's surface. |
