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Understanding Earthquakes: Causes, Waves, and Measurement Mechanisms

This resource provides a comprehensive overview of earthquakes, aimed at 5th-grade students. It explains what an earthquake is, detailing the processes of rock slipping and breaking along faults, the different types of faults, and the tectonic movements that cause earthquakes. The document also covers seismic waves—Primary (P) waves, Secondary (S) waves, and surface waves—discussing their characteristics and how they help in locating earthquakes. Additionally, it introduces measurement scales, such as the Richter and Mercalli scales, along with a brief mention of tsunamis.

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Understanding Earthquakes: Causes, Waves, and Measurement Mechanisms

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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? • The slipping and breaking of rock material along a fault. • Faults are “cracks” in the crust near plate boundaries that are under stress. • Stress is caused by the heat within the earth trying to escape and the movement of the plates.

  3. Three Types of Faults Strike-Slip - shearing Thrust - Compression Normal – pulling away

  4. What causes earthquakes? • Tectonic plates move past each other causing stress. Stress causes the rock to deform • Plastic deformation – does not cause earthquakes • Elastic deformation – rock stretches then reaches a breaking point, releasing energy – kind of bounces back like a rubberband.

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

  8. 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

  9. 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

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

  11. Comparing Seismic Waves

  12. 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

  13. 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

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

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

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

  17. Earthquake Waves & Earth’s Interior

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

  19. How are Earthquakes Measured? Richter Scale

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

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

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

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

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