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Learning Targets

Learning Targets

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Learning Targets

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  1. Learning Targets • By the end of this unit, you should be able to: • Discuss stress and strain and their roles in earthquakes • Identify and describe the 3 types of faults • Know the differences between elastic and plastic deformations • Know the 3 types of waves and how they are different from each other • Vocabulary from Chapter 11 in your book

  2. What are Earthquakes? • The shaking or trembling caused by the sudden release of energy • Usually associated with faulting or breaking of rocks

  3. Stress and Strain • Stress occurs when there is a force on the rocks. • Strain is the response to stress • 1. Compression-squeeze together • 2. Tension-pull apart • 3. Shear- Slide Past

  4. Stress Strain Curve • Elastic deformation- low stress, material bends and stretches (pulling of rubber band-goes back into shape • Plastic deformation- stress builds past elastic point, causes permanent deformation • Failure - occurs when there is a rupture (Break)

  5. Stress Strain Curve

  6. Faults • Crack in the earth where plates moves • Reverse Fault • Land being PUSHED together • Seen at convergent boundaries

  7. Normal Fault • Land PULLING apart • Caused by tension • Divergent boundary

  8. Strike Slip Fault • Also known as a transform fault • Land block SLIDING PAST each other (Caused by horizontal sheering) • Example • San Andreas Fault in California

  9. What are Seismic Waves? • Energy that is released by an earthquake • Energy travels in the form of waves • Three types: • P-waves (Primary) • S-waves (Secondary) • Surface Waves

  10. P and S waves • P or primary waves • fastest waves • travel through solids, liquids, or gases • compression wave, material movement is in the same direction as wave movement

  11. S or secondary waves • slower than P waves • travel through solids only • shear waves - move material perpendicular to wave movement

  12. Surface Waves • Surface Waves • Travel just below or along the ground’s surface • Slower than body waves; rolling and side-to-side movement • Especially damaging to buildings

  13. The Focus and Epicenter of an Earthquake • Focus • The point within Earth where faulting begins is the focus---below the surface • Epicenter • The point directly above the focus on the surface

  14. Clues to Earth’s Interior • Earth’s internal structure • Waves change speed and direction depending on the material they go through • S Waves do not go through the outer core • When the waves change scientists can gain information about the consistency and density of our earth’s layers • Shadow zone is created where no P or S waves travel

  15. How are the Size and Strength of an Earthquake Measured? • Magnitude • Richter scale measures total amount of energy released by an earthquake; independent of intensity • Intensity • Modified Mercalli Scale • subjective measure of the kind of damage done and people’s reactions to it

  16. Where Do Earthquakes Occur and How Often? • ~80% of all earthquakes occur in the Ring-of-Fire • most of these result from convergent margin activity • more than 150,000 quakes strong enough to be felt are recorded each year

  17. The Economics and Societal Impacts of EQs Damage in Oakland, CA, 1989 • Building collapse • Fire • Tsunami • Ground failure