| A | B |
|---|
| earthquake | the shaking and trembling that result from the movement of rocks beneath earth’s surface . |
| Focus | is the area beneath Earth’s surface where rock that is under stress ,break, triggering an earthquake. |
| Epicenter | the point on the surface directly above the focus. |
| p waves | are seismic waves that compress and expand the ground like an accordion. |
| S waves | are seismic waves that vibrate from side to side as well as up and down. |
| Surface waves | move more slowly than p waves and s waves reach the surface |
| Mercalli scale | was developed to rate earth quakes according to the level of damage. |
| Magnitude | is the number that geologists assign to an earthquake based on the earthquake’s size. |
| Richter scale | is a rating of an earthquake’s magnitude based on the earthquake’s seismic waves . |
| Seismograph | an instrument that records and measures seismic waves |
| Moment Magnitude scale | a rating system that estimates the total energy released by an earthquake. |
