CMDV+2.2

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=2.2 Measuring Earthquakes=

Vocabulary

 * Focus:** The point beneath Earth's surface where rock that is under stress breaks, triggering an earthquake.
 * Epicenter:**The point on the surface directly above the focus.
 * P waves:** earthquake waves that compress and expand the ground.
 * S waves:** earthquake waves that vibrate from side to side as well as up and down.
 * Seismic waves:** vibrations that travel through Earth carrying the energy released during an earthquake.
 * Surface waves:** Produces the most severe ground movements.
 * Seismograph:** Records ground movements caused by seismic waves as they move through the earth.
 * Magnitude:** A measurement of earthquake strenghth based on seismic waves and movement along faults.
 * Mercalli scale:** Was develpoed to rate eartquakes according to their intensity.
 * RItcher scale:** A ranging of the siize of seismic waves as measured by a particular type oof mechanical seismograph.
 * Moment magnitude scale:** a rating system that estimates thhe total energy released by an earthquake.

Seismic Waves

 * Seismic waves carry the energy of an earthquake away from the focus, through the Earth's interior, and across the surface.
 * There are three categories of seismic waves: P waves, S waves, and surface waves.
 * Primary Waves
 * Secondary Waves
 * Surface Waves

Measuring Earthquakes

 * The Mercalli Scale
 * The Richter Scale
 * The Moment Magnitude Scale