| A | B |
|---|
| focus | point beneath Earth's surface where rock breaks under stress & 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 the energy released during an earthquake |
| P waves | a type of seismic wave that compresses and expands the ground |
| S waves | a type of seismic wave that moves the ground up and down or side-to-side |
| surface wave | a type of seismic wave that forms when P waves & S waves reach Earth's surface |
| 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 |
| moment magnitude scale | a scale that rates earthquakes by estimating the total energy released by an earthquake |
| earthquake | the shaking that results from the movements of rock beneath Earth's surface |
| stress | a force that acts on rock to change its shape or volume |
| shearing | stress that pushes a mass of rock in opposite directions |
| tension | stress that stretches rock so that it becomes thinner in the middle |
| compression | stress that squeezes rock until it folds or breaks |
| deformation | a change in the volume or shape of Earth's crust |
| fault | a break in Earth's crust where slabs of rock slip past each other |
| strike-slip fault | a type of fault where rocks on either side move past each other sideways with little up-or-down motion |
| normal fault | a type of fault where the hanging wall slides downwards;caused by tension in the crust |
| hanging wall | the block of rock that forms the upper half of a fault |
| footwall | the block of rock that forms the lower half of a fault |
| reverse fault | a type of fault where that hanging wall slides upward |
| fault-block mountain | a mountain that forms where a normal fault uplifts a block of rock |
| folds | a bend in the rock that forms where part of Earth's crust is compressed |
| anticline | an upward fold in rock formed by compression of Earth's crust |
| syncline | a downward fold in rock formed by compression in Earth's crust |
| plateau | a large area of flat land elevated high above sea level |
