| A | B |
|---|
| EARTHQUAKE | The shaking that results from the movement of rock beneath Earth's surface. |
| 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 WAVES | A vibration that travels through Earth carrying energy released during an earthquake. |
| P WAVES | A type of seismic wave that compresses and expands the ground; parallel waves. |
| S WAVES | A type of seismic wave that moves the ground up and down or side-to-side; transverse waves. |
| SURFACE WAVES | A type of seismic wave that forms when P waves and S waves reach Earth's surface. |
| SEISMOGRAPH | A device that records ground movement caused by seismic waves as they move through Earth. |
| 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 mechanical seismograph. |
| MOMENT MAGNITUDE SCALE | A scale that rates earthquakes by estimating the total energy released by an earthquake. |
| LIQUEFACTION | The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud. |
| AFTERSHOCK | An earthquake that occurs after a larger earthquake in the same area. |
| TSUNAMIS | A giant wave caused by an earthquake on the ocean floor. |
| BASE-ISOLATED BUILDING | A building mounted on bearings designed to absorb the energy of an earthquake. |
