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Earthquakes

Earthquakes. Liz LaRosa http://www.middleschoolscience.com 2009 for my 5 th grade science class 2009. What is an earthquake?. Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip

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Earthquakes

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  1. Earthquakes Liz LaRosa http://www.middleschoolscience.com 2009 for my 5th grade science class 2009

  2. What is an earthquake? • Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip • Caused by volcanic or magmatic activity, • Caused by other sudden stress changes in the earth.

  3. Types of Faults Strike-Slip Dip Slip

  4. What causes earthquakes? • Tectonic plates move past each other causing stress. Stress causes the rock to deform • Elastic deformation – rock stretches then reaches a breaking point, releasing energy.

  5. Elastic Rebound – deformed rock goes back to its original shape http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  6. Focus – point inside the Earth where an earthquake beginsEpicenter – point on Earth’s surface above focus

  7. Primary Waves (P Waves) • A type of seismic wave that compresses and expands the ground • The first wave to arrive at an earthquake http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

  8. Secondary Waves (S Waves) • A type of seismic wave that moves the ground up and down or side to side http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

  9. Comparing Seismic Waves

  10. Surface Waves • Move along the Earth’s surface • Produces motion in the upper crust • Motion can be up and down • Motion can be around • Motion can be back and forth • Travel more slowly than S and P waves • More destructive

  11. How do scientists calculate how far a location is from the epicenter of an earthquake? • Scientists calculate the difference between arrival times of the P waves and S waves • The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

  12. How are Earthquakes Measured? Richter Scale

  13. How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf

  14. Earthquake Waves & Earth’s Interior

  15. Tsunamis http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  16. Formation of a tsunami http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

  17. Tsunami Warning System http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

  18. Magnitude 7.0 PERUWednesday, September 25, 2013 at 16:42:42 UTC The Nazca Plate subducts beneath the South America plate at the Peru-Chile Trench offshore of western South America.    At the latitude of the earthquake, the Nazca Plate moves to the east-northeast with respect to the South America Plate with a velocity of about 70 mm/y.  South American Plate Peru-Chile Trench Nazca Plate

  19. Magnitude 7.0 PERUWednesday, September 25, 2013 at 16:42:42 UTC The record of the earthquake on the University of Portland seismometer (UPOR) is illustrated below. Portland is about 8355 km (~5192 miles, 75.27 degrees) from the location of this earthquake. P-waves are compressional waves that travel a curved path through the mantle. The P-waves arrived to the seismometer in Portland 11 minutes and 44 seconds (704 seconds) after the earthquake. PP waves are compressional waves that bounce off the Earth’s surface halfway between the earthquake and the seismic station. Traveling the same path as the P-wave, the S-waves (shear waves) travel at a slower velocity, arriving 21 minutes and 25 seconds (1285 seconds) after the earthquake. The surface waves are the last to arrive approximately 39 minutes after the earthquake, having traveled 8355 km to Portland along the surface of the Earth.

  20. Magnitude 7.0 PERUWednesday, September 25, 2013 at 16:42:42 UTC Shaking Intensity The Modified Mercalli Intensity (MMI) scale depicts shaking severity. The area nearest the earthquake experienced strong shaking. Perceived Shaking Extreme Violent Severe Very Strong Strong Moderate Light Weak Not Felt Modified Mercalli Intensity USGS Estimated shaking Intensity from M 7.0 Earthquake Image courtesy of the US Geological Survey

  21. Magnitude 7.0 PERUWednesday, September 25, 2013 at 16:42:42 UTC This region experiences a large number of earthquakes.  Within 250 km of the epicenter, there have been 17 earthquakes of M6 and larger since 1973. The largest, a M8.4 earthquake of June 23, 2001, occurred along the plate boundary to the south.  It killed at least 74 people and destroyed over 17,000 homes.  Earthquakes are shallow at the Peru-Chile Trench and increase to > 500 km depth towards the east as the Nazca Plate subducts deeper beneath the South American Plate. Earthquake

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