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EARTHQUAKES

EARTHQUAKES. Section 21.2. What is an earthquake?. WHAT IS AN EARTHQUAKE? An earthquake is a movement of Earth’s crust caused by a release of energy  . WHAT CAUSES AN EARTHQUAKE? Eruption of a volcano Collapse of a cavern or building Major cause – stress between two plates.

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EARTHQUAKES

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  1. EARTHQUAKES Section 21.2

  2. What is an earthquake? WHAT IS AN EARTHQUAKE? • An earthquake is a movement of Earth’s crust caused by a release of energy   WHAT CAUSES AN EARTHQUAKE? • Eruption of a volcano • Collapse of a cavern or building • Major cause – stress between two plates

  3. Where do EQ’s occur in the world?

  4. They occur along Plate Boundaries

  5. Where do EQ’s occur in the U.S.?

  6. What Causes Earthquakes? • Friction builds up between two plates • The stress causes the plates to deform or ‘stretch’ • Eventually, the stress becomes great enough that it overcomes friction and the plates move • The plates ‘snap’ back into their original shape and begin building up friction again

  7. Damage from a 1906 EQ

  8. What is the Focus of an EQ? • Point on the fault (or plates) where movement first occurs • Where an earthquake starts • 3 types • Shallow (0-70km) • Intermediate (71-300km) • Deep (301km and higher)

  9. Epicenter • Point on the Earth’s surface directly above the focus • What is reported as the location of an earthquake

  10. Earthquake waves • P-waves: primary waves; travel through solids, liquids, and gases; back and forth motion • P waves are ______________ waves.

  11. Earthquake waves • S-waves: secondary waves; travel through solids only; side to side motion (snake) • S waves are ___________ waves

  12. Earthquake waves • L-waves: surface waves • Combination of up and down and back and forth motion • Cause the most damage due to their rolling action and long wavelengths

  13. EARTHQUAKE!

  14. EQ wave Diagram

  15. Locating an earthquake • Seismograph: an instrument that detects and records earthquake waves • P-waves always arrive first, then S-waves, then L-waves

  16. Determining distance to the epicenter • P and S Waves Graph – pg.767 – Under Graphing Skills • As distance increases, the travel time for seismic waves increases also.

  17. Locating an Epicenter • To locate the exact location of an epicenter, you must have points from three separate seismograph locations around the world

  18. Earthquake Magnitude • Richter Scale • Developed by Charles Richter in the 1940’s • Measures the amount of energy released by the earthquake itself • Scale from 1-10 (weakest - strongest) • Each number is 32 times stronger than the next lower number (Ex: ‘6’ is 32 times stronger than a ‘5’ and 1024 times stronger than a ‘4’)

  19. Earthquake Prediction • We cannot predict earthquakes other than giving periods of time in which we think they will occur. • Earthquakes are most common along sliding plate boundaries, but they can occur in other places. • http://earthquake.usgs.gov/learn/kids/

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