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EQ notes 25.2. Earthquake -A sudden movement or vibration of the ground that occurs when rocks slip or slide along cracks in the Earth - corresponds closely with plate boundaries -usually shallow EQ’s (70km or lower) occur at divergent boundaries
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EQ notes 25.2 Earthquake -A sudden movement or vibration of the ground that occurs when rocks slip or slide along cracks in the Earth - corresponds closely with plate boundaries -usually shallow EQ’s (70km or lower) occur at divergent boundaries -deep EQ’s (70km or more) occur at convergent boundaries
FAULTS -crack in the Earth’s crust where rock has moved CAUSES -Energy is released along a fault -caused by forces applied to rocks along plate boundaries
DEFORMATION 4 types of STRESS 1- compression (comes together) -Caused by forces applied to objects -Stress on a object is the force/unit area that acts on that object 2- tension (pulls apart) 3- shearing (moves opposite ways) 4- torsion (twists)
Types of deformation Elastic deformation occurs when stress is applied and the object snaps back to its original shape. Plastic or Inelastic deformation occurs when stress is applied and the object DOES NOT snap back to original position
ENERGY RELEASE Elastic Rebound- EQ occur when a rock that has been stressed releases strain energy and moves along the fault. SEISMIC WAVES • Point of ORIGIN from an EQ is called the FOCUS • Point on SURFACE above focus is the EPICENTER Surface Waves- move both horizontally and vertically EX ocean waves
SEISMIC WAVES CONT. S-waves (secondary)- Transverse waves move materials at right angles to the wave direction. EX- a rope P-waves (primary)- Compressional waves that, move through material by squeezing and stretching the material in the same direction as the wave is moving.EX- a spring http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm
EQ MEASUREMENT Mercalli Scale- measures EQ intensity Richter Scale- magnitude scale, measures the energy released during an EQ Seismograph- records ground vibration during an EQ
EQ DAMAGE • Nearly all EQ damage comes from buildings and human made objects. • Can cause tsumanis • In the middle of nowhere an EQ does not cause much damage at all