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Vocabulary

 * focus**- the point under Earth's surface where rock that is under stress breaks and creates an earthquake.


 * epicenter**- the point directly beneath the focus, which gets the most severe damage when an earthquake happens.


 * seismic waves**- vibrations that travel through the Earth carrying energy released from an earthquake.


 * primary waves**- also called "P- waves", these waves are the first waves to arrive. P- waves are earthquake waves that compress and expand the ground, stretching the Earth's crust like an accordion being played.


 * secondary waves** also called "S- waves", these waves are second to arrive (primary waves being the first). S waves are waves that vibrate side by side as well as up and down. Unlike P- waves, which can through liquids as well as solids, S- waves cannot pass through liquids.


 * surface waves**- after P- waves and S- waves reach the surface, some of them turn into surface waves. Although they move slower than P- waves and S- waves, they create the most serious ground movements.


 * Magnitude**- a measurement of earthquake strength based on seismic waves around faults.


 * Mercalli Scale**- A scale developed to rate earthquakes based on their intensity.


 * Richter Scale**- A scale that is based on the size of the seismic waves as recorded by a seismograph.


 * Moment Magnitude Scale**- A scale that estimates the total energy released by an earthquake, near or far, big or small.


 * Outline**

T= Measuring Earthquakes 1. primary Waves 1. secondary waves 1. surface waves 1. Detecting Seismic Waves 1. Measuring Earthquakes 1. Locating the Epicenter
 * focus[[image:file:GWBN2.2.psd%20@%20100%25%20%28RGB%29.jpg]]
 * place where rock breaks
 * epicenter
 * place directly above the focus
 * most severe shaking in earthquake
 * 1. Seismic Waves [[image:GWBN2.2.psd_@_100%_(RGB)-2.jpg width="216" height="174" caption="The fault, the epicenter, the focus and seimic waves"]]
 * vibrations that travel through earth
 * carrying energy released from earthquake
 * carry the energy of earthquake
 * away from the focus
 * through Earth's interior
 * and across the surface
 * energy released= greatest at epicenter
 * three types of seismic waves
 * P- waves
 * S- waves
 * surface wave
 * also p- waves
 * waves that compress + expand ground
 * can cause buildings to expand and contract
 * waves rock up+ down, side+ side
 * shake structures violently
 * cannot go through liquids
 * when p- waves, s- waves reach surface
 * some become surface waves
 * slower than P- waves, S- waves
 * make most severe ground movement
 * some roll like ocean waves
 * some shake from side to side
 * Seismographs used to find waves
 * record ground movement
 * built by wire attached to pen
 * on a piece of paper
 * pen shakes, and paper records it
 * bigger the waves on paper, bigger earthquake
 * Three ways of measuring earthquakes
 * Mercalli Scale
 * Richter Scale
 * Moment Magnitude Scale
 * magnitude
 * measurement of earthquake strength
 * based on seismic waves
 * and movement of fault
 * The Mecalli Scale
 * rate earthquakes by intensity
 * intensity= strength of ground motion
 * not a precise measurement
 * 12 steps
 * The Richter Scale
 * rating size of seismic waves
 * based on seismograph
 * accurate measurements for nearby, earthquakes
 * inaccurate for big, distant earthquakes
 * The Moment Magnitude Scale
 * Used by geologists today
 * rate earthquakes big or small
 * near or far
 * 5.0= little damage
 * above 5.0= big destruction
 * seismic waves enter at different speeds
 * first are p- waves
 * then s- waves
 * farther earthquake, greater time between waves