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Earthquakes – Earth Science

Earthquakes – Earth Science. What is an Earthquake?. Earthquakes occur along (within) faults . These represent fractures (zones of weakness) within the brittle rocks that makeup the crust of our planet.

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Earthquakes – Earth Science

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  1. Earthquakes – Earth Science

  2. What is an Earthquake? Earthquakes occur along (within) faults. These represent fractures (zones of weakness) within the brittle rocks that makeup the crust of our planet. It is the abrupt rupture or movement along these structures that triggers an “earthquake”. These phenomena rarely last even 1 minute yet are responsible for the greatest number of lives lost (and property damage) due to a natural event!

  3. What is an Earthquake? TYPES OF FAULTS Strike-slip Thrust Normal The form of faulting depends upon the type of plate motion and nature of rocks.

  4. The actual underground location of the earthquake is called the focus. The location on the surface directly above is called the epicenter.

  5. Earthquakes happen in some areas more than others, usually close to plate boundaries.

  6. Seismic WavesWhen an earthquake occurs, the energy is dissipated into the surrounding medium through seismic waves.Earthquakes create seismic waves which shake the ground as they pass. Earthquakes create waves just like waves of water moving across the ocean and waves of air moving across a field of wheat.

  7. Seismic WavesConsider what happens when a drop of rain hits a pond of water. The drop disturbs the flat surface of the water and creates waves that travel outward in all directions from the disturbance. These waves travel on the surface of the pond, along the interface between the water and the air.

  8. HOW IS THE ENERGY DISPERSED “SPREAD” INTO THE SURROUNDING MEDIUM? Seismic wavesare the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.

  9. Types of Seismic Waves There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves arebody wavesand surface waves. Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.

  10. BODY WAVES P-waves; also known as primary waves or pressure waves S-waves; also referred to as secondary or shear waves SURFACE WAVES Love and Raleigh waves

  11. 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

  12. 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

  13. Comparing Seismic Waves

  14. 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

  15. SURFACE WAVES (Theses produce all the damage!)

  16. Which wave to the right is like a P-wave? Which wave to the right is like a S-wave?

  17. How Seismographs Work the pendulum remains fixed as the ground moves beneath it http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  18. Typical Seismogram http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

  19. 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

  20. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  21. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  22. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

  23. HOW IS EARTHQUAKE INTENSITY MEASURED? There are currently two “measuring” schemes used to “quantify” or “qualify” the destructiveness or power of an earthquake. 1) The Mercalli Intensity scale (it is qualitatively based) 2) The Richter Magnitude scale (it is quantitatively based)

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

  25. How are Earthquakes Measured? Richter Scale

  26. Earthquake Waves & Earth’s Interior

  27. Seismic Waves in the Earth http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

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

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

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