AUFC+2.2

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Vocabulary

 * focus**: the area under the Earth's surface where rock that is under stress breaks, causing an earthquake
 * epicenter**: the area on the surface that is above the focus
 * seismic waves**: vibrations that travel through Earth carrying energy released during and earthquake
 * 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
 * surface waves**: they move more slowly than P waves and S waves, but theground movements
 * seismograph**: records the ground movement caused by seismic waves as they move through the Earth
 * magnitude**: a measurement of earthquake strength based on seismic waves and movement along faults
 * Mercalli Scale**: rates earthquakes according to their intensity
 * Richter Scale**: a rating of the size of seismic waves as measured by a particular type of mechanical seismograph
 * moment magnitude scale**: a rating system that estimates the total energy released by and earthquake

Seismic Waves

 * sound waves carry force as they move away from their origin
 * during earthquake, seismic waves come out from focus in every way
 * three categories for seismic waves; P waves, S waves, and Surface waves

Primary Waves

 * first waves to come in from core
 * makes buildings become bigger and smaller
 * can travel through solids and liquids

Secondary Waves

 * comes after P waves
 * moves ground back and forth
 * shakes buildings violently
 * can't go through liqueds

Surface Waves

 * when P waves and S waves reach surface, they turn into surface waves
 * moves slower than P waves and S waves
 * has the strongest ground movements

Detecting Seismic Waves

 * to measure seismic waves, scientists use seismographs

Measuring Earthquakes

 * the three types of scales are...
 * the Mercalli scale
 * the Richter scale
 * the Moment Magnitude scale

Mercalli Scale

 * was invented on early 20th century
 * it doesn't give the exact measurement
 * there are 12 steps that describe how earthquakes affect people, buildings, and land surface
 * the same type of earthquake can have different Mercalli ratings because it is in a different location

Richter Scale

 * invented in 1930's
 * used for about 50 years
 * provides correct measurements for small and close earthquakes
 * scale does not work well for large or far earthquakes

Moment Magnitude Scale

 * used to measure earthquakes of all sizes, both close and far away earthquakes

Locating the Epicenter
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 * use seismic waves to find the epicenter
 * to find epicenter, measure between arrival times of P waves S waves
 * the farther the epicenter, the farther the amount of time there is between the arrival times of the P waves and S waves