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Chapter 10: Earthquakes (Part 3)

Chapter 10: Earthquakes (Part 3). IN-CLASS EXERCISE. Observe the following objects as I drop them on the floor and answer the following questions: Objects: - Clay - Rubber Ball Ice Cube Questions: 1) Which of these behaves as a brittle material? 2) As a ductile material?

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Chapter 10: Earthquakes (Part 3)

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  1. Chapter 10:Earthquakes (Part 3)

  2. IN-CLASS EXERCISE • Observe the following objects as I drop them • on the floor and answer the following questions: • Objects: • - Clay • - Rubber Ball • Ice Cube • Questions: • 1) Which of these behaves as a brittle material? • 2) As a ductile material? • 3) As an elastic material? • 4) Which of these material properties best accounts • for the generation of earthquakes?

  3. Optional extra credit assignment (20 pts): The just released movie “The Core” is loaded with geology, some of it accurate and some not! Assignment: Go and see “The Core” and write a report that separates geological fact from fiction! Length of write-up: 2 pages Use illustrations. Due two weeks from today.

  4. TODAY’S LECTURE • Detecting earthquakes. • Determining earthquake intensity and magnitude. • Locating earthquakes. • Earthquake damage (with examples).

  5. P-wave S-wave Surface-wave In summary: Types of seismic waves Motion produced by the different wave types

  6. Fig. 10.17 Arrival times of earthquake waves. W. W. Norton

  7. seismic waves Ancient Chinese seismograph Instrument to record seismic waves Seismology Seismology - The study of earthquake “waves”, earthquakes, Earth Seismogram- Recording of ground shaking from seismographs

  8. Fig. 10.15 Seismograph vs. seismogram W. W. Norton

  9. Electrostatic device: Fig. 10.16 W. W. Norton

  10. For measuring vertical motion… For measuring horizontal motion…

  11. Earthquake Intensity and Magnitude • Mercalli Intensity Scale • Magnitude Qualitative scale to convey intensity of ground Shaking & damage at a specific location Depends on distance to earthquake. & strength of earthquake. An absolute measure of the energy released in an earthquake Depends on the amount of elastic energy stored in the rocks prior to the earthquake and the intensity of faulting to release that energy.

  12. Earthquake Magnitude & Intensity • Magnitude • Intensity An absolute measure of the energy released in an earthquake. A qualitative measure of intensity based on damage. Magnitude Intensity

  13. Fastest wave: Arrives first! Basic Approach: Measure time between P and S wave on seismogram. Use travel-time graph to get distance to epicenter. Draw circle on a map with radius of that distance. Three or more circles should intersect at epicenter! Locating an Earthquake… P-waves & S-wave travel at different speeds…

  14. Fig. 10.18ab W. W. Norton

  15. Locating an Earthquake… 1. Measure time between P and S wave on seismogram. 2. Use travel-time graph to get distance to epicenter. 3. Draw circle on a map with radius of that distance. 4. Three or more circles should intersect at EQ!

  16. Fig. 10.18c W. W. Norton

  17. Fig. 10.20

  18. Earthquake Magnitude & Intensity • Magnitude An absolute measure of the energy released in an earthquake. Magnitude is measured at focus and is a non-linear scale… That is, the increase in energy between each step is exponential. Magnitude Intensity

  19. Fig. 10.21

  20. Earthquake Damage San Francisco, 1906

  21. San Francisco 1906 Earthquake: Magnitude 8.3 Intense fire damage area

  22. San Francisco 1906 Earthquake: Magnitude 8.3

  23. Fig. 10.13ef W. W. Norton

  24. San Francisco 1906 Earthquake: Magnitude 8.3

  25. San Francisco 1906 Earthquake: Magnitude 8.3

  26. San Francisco 1906 Earthquake: Magnitude 8.3

  27. San Francisco 1906 Earthquake: Magnitude 8.3

  28. Chapter 10:Earthquakes (Part 4)

  29. Midterm 2 is this Friday! Will cover these text chapters & lectures: CLASS ANNOUNCEMENTS • Chapter 7 (Sedimentary Rocks): Pages 188-199. • Chapter 8 (Metamorphic Rocks) • Interlude B (Rock Cycle) • Chapter 9 (Volcanoes) • Chapter 10 (Earthquakes) • Interlude C (Seeing inside the Earth) • Chapter 11 (Crustal deformation and mountain building): Pages 319-334. ~50 MC questions. Worth 100 pts. Review outline will be Posted on web this evening.

  30. TODAY’S LECTURE • Earthquake damage (with examples). • Factors that determine the intensity of an earthquake. • Secondary effects of earthquakes. • Videos on selected eartquakes. • Quiz on Chapters 9 and 10.

  31. Earthquake Destruction • Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design • Other undesirable effects: Landslides 2) Liquifaction of sediments 3) Fires (rupture of gas lines) 4) Tsunamis (seismic sea waves)

  32. Fig. 10.36a W. W. Norton

  33. Fig. 10.36b W. W. Norton

  34. Fig. 10.36c W. W. Norton

  35. Earthquake hazards Along Passive Margins Fig. 10.19 Charleston, S.C. August 1886 Death toll: 60. Magnitude: ~7 W. W. Norton

  36. What happened? Large Intraplate Earthquakes… New Madrid, Missouri, 1811-12 • Accounts from fur trappers • & naturalist, John Audubon. • Estimated magnitude: >8.5 • Three main shocks. • 1500 aftershocks. • Activity lasted 53 days. • Affected >2.5 million sq. km (1 million acres) • Church bells tolled in Boston. • Windows rattled, Washington D.C. • Thousands of sq. km. subsided to form lakes (St. Francis & Reelfoot Lakes). • Large swamps were formed. • Mississippi River reversed flow in places. • Waves overwhelmed riverboats. • Large fissures opened on flood plain of river. • Geysers of sand, water and sulfurous geysers were erupted.

  37. Earthquake Destruction • Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design • Other undesirable effects: Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

  38. Fig. 10.38d

  39. Earthquake Destruction • Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design • Other undesirable effects: Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

  40. High Rise Buildings W. W. Norton Vertical and horizontal ground motion

  41. Mexico City, 1985

  42. Taiwan, 1999 Magnitude 7.6

  43. Collapse of Smaller Multistory Buildings Fig. 10.27ab W. W. Norton Collapse of Building Facades

  44. Northridge, CA. 1994 Magnitude: 6.7 Deaths: 61 Fig. 10.28c J. Dewey, U.S. Geological Survey Collapse of first floor parking structures

  45. Collapse of Building Facades Seattle 2/28/2001 Magnitude 6.8

  46. Types of Earthquakes Aftershocks Small earthquakes that follow an initial earthquake in same vicinity Foreshocks Small earthquakes that sometimes precede a large one by few days

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