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Earth Science

Earth Science. Coach Williams Room 310B. Chapter 19. Earthquakes. Section 19.1: Forces Within the Earth. Objectives: Define stress and strain as they apply to rocks Distinguish among the three types of faults Contrast three types of seismic waves. Earthquakes. Vibrations of ground

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Earth Science

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  1. Earth Science Coach Williams Room 310B

  2. Chapter19 • Earthquakes

  3. Section19.1: Forces Within the Earth • Objectives: • Define stress and strain as they apply to rocks • Distinguish among the three types of faults • Contrast three types of seismic waves

  4. Earthquakes • Vibrations of ground • Caused by movement along fractured crust

  5. Stress and Strain • Stress: forces that act on a material • Compression: decreases volume of material • Tension: pulls material apart • Shear: causes materials to twist • Strain: deformation of material due to stress

  6. Faults • Fault: fracture in crust; caused by stress • Reverse: horizontal compression (pushing together) • Normal: horizontal pulling apart • Strike-Slip: shear forces (sideways)

  7. Faults

  8. Earthquake Waves • Primary (P-waves): rocks move in same direction as waves. • Secondary (S-waves): rocks move @ right angles to direction of wave. • Surface: rocks move in 2 directions • Surface waves stay on surface • S/P Waves pass through interior (body waves)

  9. Earthquake Waves

  10. Earthquake Waves

  11. Focus & Epicenter • Focus: point where Earthquakes start • Usually below surface • Epicenter: point directly above on surface

  12. Section 19.2: Seismic Waves and Earth’s Interior • Objectives: • Describe how a siesmometer works • Explain how seismic waves have been used to determine the structure and composition of Earth’s interior

  13. Seismometers and seismograms • Seismology: study of earthquake waves • Surface and interior • Seismometer: detects/records seismic waves • Seismogram: record of waves

  14. Seismometers

  15. Travel-Time Curve • Many earthquakes are charted • Shows time an distance from epicenter • Determines distance

  16. Clues to Earth’s Interior • Changing speed/direction of waves • P-waves diffracted • S-waves won’t go through liquid

  17. Earth’s Interior

  18. Section 19.3: Measuring and Locating Earthquakes • Objectives: • Compare/contrast earthquake magnitude and intensity and the scales used to measure each • Explain why data from at least three seismic stations are needed to locate an earthquake’s epicenter • Describe Earth’s seismic belts

  19. Magnitude and Intensity • Magnitude: amount of energy released • Depth affects magnitude • Richter scale: • Measured magnitude • Largest wave • Power of 10 (8 is 10x larger than 7 & 100x more than 6) • Moment Magnitude Scale • Fracture length and movement • Modified Mercalli Scale • Amount of damage (intensity) • I-XII

  20. Magnitude and Intensity

  21. Magnitude and Intensity

  22. Locating an Earthquake • Distance from 3 seismic stations • Intersecting 3 circles

  23. Locating an Earthquake

  24. Seismic Belts • Plotted earthquakes • Regions

  25. Section19.4: Earthquakes and Society • Objectives: • Discuss factors that affect eh amount of damage done by an earthquake • Explain some of the factors considered in earthquake probability studies • Define seismic gaps

  26. Earthquake Hazards • Structure failure • Buildings (pancaking), building materials? • Land/Soil failure • Landslides, soil liquefaction • Fault scarps: ground deformations • Tsunami: large ocean wave

  27. Fault Scarp

  28. Landslide

  29. Tsunami

  30. Tsunami

  31. Seismic Risk

  32. Earthquake Prediction • Earthquake history: • Intervals (Parkfield, CA- 22years) • Seismic gaps: time since last earthquake • Strain accumulation: measure of strain

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