BCJS+2.2

= = toc =Chapter 2.2=

Vocabulary

 * Focus:** the exact location under the earth's crust where the rock breaks from stress, triggering an earthquake
 * Epicenter:** point that is on the earth's surface, directly above the focus
 * Seismic Waves:** vibrations moving with energy caused by an earthquake
 * P waves:** seismic waves that compress/expand the ground
 * S waves:** seismic waves that make the ground shake violently, vibrating in all directions
 * Surface Waves:** slowest of seismic waves, but causes most damage
 * Seismograph:** records the movement in the ground made by seismic waves
 * Magnitude:** the measurement for an earthquake's strength
 * Mercalli Scale:** machine that rates earthquake's intensity
 * Richter Scale:** machine that rates size of seismic waves
 * Moment Magnitude Scale:** machine that estimates all the energy that was released when an earthquake occured

Measuring earthquakes

 * **Seismic Waves = Energy of the Earth**
 * **Primary Waves**
 * The fastest of the waves
 * These waves stretch and compress the ground
 * They make the ground move forward and back only
 * **Secondary Waves**
 * Comes after primary waves
 * Makes the ground move up and down, left to right
 * This type of wave cannot go through liquids
 * **Surface Waves**
 * The slowest of the waves
 * But, it is the most violent wave of the waves
 * **Detecting Seismic Waves**
 * **Measuring Earthquakes**
 * **Mercalli Scale**
 * The scale which is measured how much damage or effects affect the area
 * This scale is not accurate because different areas can have different damages
 * **Richter Scale**
 * The Richter Scale was used for 50 years
 * It needed a special kind of seismograph
 * It was not accurate because it could not defer large or distant earthquakes
 * **Moment Magnitude Scale**
 * This scale is the most accurate
 * This scale uses more accurate seismographs, electric ones
 * **Locating the Epicenter**