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Identify causes of earthquakes Distinguish between S waves, P waves, and surface waves Describe how earthquakes are measured and rated Triangulate to find the location of an earthquake Discuss the types of damage that can occur
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Earthquakes are vibrations caused by movement of rocks sliding past each other.
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These movements of rocks are more common at plate boundaries California and Japan have many earthquakes because they are on plate boundaries.
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RankDateLocationMagnitudeEstimated Deaths/Damages (USD) 11960Chile9.51,655/$6 million 21964Alaska9.2128/$300 million 32004W. Sumatra9.1 227,898/estimated in the billions 41952Russia9.1none reported/$1 million 51906Ecuador8.8500-1500/unknown 61965Alaska8.7none reported/$10,000 72005N. Sumatra8.61300/unknown 81950Tibet8.6780/$25 million 91957Alaska8.6none reported/$5 million 102007S. Sumatra8.521/unknown
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In terms of magnitude it won’t be in the top 10 Magnitude 7.0 In terms of destruction and loss of life it will Already 80,000 buried in mass graves The number dead may reach over 200,000
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Let’s take a look around Port-Au-Prince
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Since the earth’s surface is in motion, rocks in the lithosphere sometimes slip past each other Well maybe slip isn’t a good word for this, maybe they GRIND past each other This Grinding caused shock waves that move through the earth
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They can move sideways They can move up and down They can push up a section They can not break the surface
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The forces build up until the fault breaks – releasing energy
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The focus is where the earthquake occurs The fault is the plane that the earth slides along The epicenter is the point on the surface above the focus – it might not be on the fault
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It looks like the needle is moving, but the earth moves under the needle
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Not all earthquakes are the same At magnitude 6, the ground moves 1 meter at the focus At magnitude 7, the ground moves 10 meters
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Primary waves Secondary waves Surface waves
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Called Primary or Longitudinal waves Compress and release Travel fastest Can travel through earth’s core but do bend (refract)
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Secondary or Transverse waves Move up and down (S shaped) Do not travel through earth’s core
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Rolling up/down or right/left Occur on surface – like ocean waves Are the most destructive
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And bounce off different layers of rock
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Found by looking at time between P waves and S waves reaching the seismograph Calculations tell you the distance to the focus It takes three seismographic measurements to triangulate where the earthquake is located
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the web site is www.sciencecourseware.com/VirtualEarthquake/ VQuakeExecute.html
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Buildings collapse Haiti Roads break up 1989 Loma Prieta Earthquake, San Fransisco Land can rise or sink 1964 Alaska, some land rose 40 feet, some seafloor dropped 50 feet Liquefaction Softer rock does not stay together, landfill is some of the worst land to build on Landslides 1692 the town of Port Royal, Jamaica slide into the ocean, it landed 50 feet below sea level Tsunamis December 26, 2004 Earthquake
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The farther away you are, the longer it takes for the tsunami to reach you, you have more time to react
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Shows debris lines on the coastline after the 2004 tsunami
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Identify causes of earthquakes Distinguish between S waves, P waves, and surface waves Describe how earthquakes are measured and rated Locate and earthquake by triangulation Discuss the types of damage that can occur
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