| A | B |
|---|
| focus | the point beneath Earth's surface where rock breaks under stress and causes an earthquake |
| epicenter | the point on Earth's surface directly above an earthquake's focus |
| seismic wave | a vibration that travels through Earth carrying the energy released during an earthquake |
| P wave | a type of seismic wave that compresses and expands the ground |
| S wave | a type of seismic wave that moves the ground up and down or side to side |
| moment magnitude scale | a scale that rates earthquakes by estimating the total energy released by an earthquake |
| seismograph | a device that records ground movements caused by seismic waves as they move through Earth |
| 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 |
| Richter scale | a scale that rates seismic waves as measured by a particular type of mechanical seismograph |
| surface wave | a type of seismic wave that forms when P waves and S waves reach Earth's surface |
