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GEOLOGY MACC Bill Palmer

GEOLOGY MACC Bill Palmer. Lecture 12 Earthquakes. GEOLOGY-Earthquakes. Probably the most terrifying geologic event Occur suddenly, often without warning May last less than 5 minutes and cause tremendous destruction Remember that Earthquakes create Tsunamis. TSUNAMI-Dec. 26, 2004

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GEOLOGY MACC Bill Palmer

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  1. GEOLOGYMACCBill Palmer Lecture 12 Earthquakes

  2. GEOLOGY-Earthquakes • Probably the most terrifying geologic event • Occur suddenly, often without warning • May last less than 5 minutes and cause tremendous destruction • Remember that Earthquakes create Tsunamis TSUNAMI-Dec. 26, 2004 300,000 killed

  3. GEOLOGY-Earthquakes • Don’t damage the land very much but destroy the built environment • We cannot control or predict with accuracy • Most powerful earthquake in lower 48 state recorded history took place in Missouri

  4. GEOLOGY-Earthquakes • Measuring Earthquakes (Two different scales) • Richter Scale • A Measure of MAGNITUDE of an Earthquake • Measured by instruments • Each number is ten times larger than preceding number • A 5 is 10X greater than a 4 • A 7 is 1000X greater than a 4 • Largest measured are 9 • Damage to structures begins at 5.5

  5. GEOLOGY-Earthquakes • Measuring Earthquakes (Two different scales) • Mercalli Scale (handout provided) INTENSITY • Measures damages to the built environment • I. Not felt • II. Felt by most people • III. Felt indoors; pictures swing • IV. Heavier objects swing, fells like passing truck • V. Felt outdoors, sleepers awake, doors swing open

  6. GEOLOGY-Earthquakes • Measuring Earthquakes (Two different scales) • Mercalli Scale • VI. Felt by all; Walk unsteady; plaster cracks; small bells ring • VII. Difficult to stand; chimneys break • VIII. Smokestacks fail; driving difficult; some walls fail • IX. Panic; Frames crack; underground pipes broken; cracks in ground; bridges fail

  7. GEOLOGY-Earthquakes • Measuring Earthquakes (Two different scales) • Mercalli Scale • X. Many buildings fail; dams damaged; landslides • XI. Rails bent; underground pipelines fail • XII. Damage nearly total, large rock masses dispalced objects thrown into air • (see handout for more details)

  8. GEOLOGY-Earthquakes • Focus and Epicenter • FOCUS-The exact place in the ground where the earthquake takes place • EPICENTER-The point on the earth’s surface directly above the focus.

  9. GEOLOGY-Earthquakes Focus and Epicenter

  10. GEOLOGY-Earthquakes • Finding the Epicenter • Earthquakes produce three types of waves • P-Travel at the fastest speed • S-Travel at medium speed • L-Travel the slowest • These waves can be measured on a Seismograph and the distance from the seismograph determined • Using THREE seismographs the exact epicenter can be determined

  11. GEOLOGY-Earthquakes The seismograph is basically a pendulum with moving paper beneath. Waves cause the pendulum to swing and the result is shown on paper Seismograph

  12. GEOLOGY-Earthquakes

  13. GEOLOGY-Earthquakes • What Mercalli rating would you give each of the earthquakes?

  14. GEOLOGY-Earthquakes • What Mercalli rating would you give each of the earthquakes?

  15. GEOLOGY-Earthquakes • What Mercalli rating would you give each of the earthquakes?

  16. GEOLOGY-Earthquakes • What Mercalli rating would you give each of the earthquakes?

  17. GEOLOGY-Earthquakes • Some infamous earthquakes-San Francisco 1906 • 3,000 dead • 225,000 homeless • 28,000 buildings destroyed

  18. GEOLOGY-Earthquakes • Some infamous earthquakes-San Francisco 1906 • Richter = 7.8-8.0 • Mercalli=8.0-9.0

  19. GEOLOGY-Earthquakes • Some infamous earthquakes-San Francisco 1906 • The damage from this earthquake was worsened by the fire that was caused when natural gas pipelines burst and caught fire.

  20. GEOLOGY-Earthquakes • Some infamous earthquakes-Alaska 1964 • Richter=9.2 • Largest in North America • Lasted 4 minutes • 10,000 aftershocks • Created 70 ft Tsunami

  21. GEOLOGY-Earthquakes Alaska-1964

  22. GEOLOGY-Earthquakes • Missouri 1811-1812 • New Madrid Earthquake • Felt over 50,000 square miles • Richter=8.0 • Seismologist estimate there is a 90% chance of a 7.0 or greater EQ in next 50 yrs

  23. GEOLOGY-Earthquakes Created Lakes-Reelfoot Bells Rang in Philadelphia Buildings in Savannah GA cracked Mississippi River course was altered Not many people in area so loss of life and damages minimal

  24. GEOLOGY-Earthquakes • Comparison of the impact of the New Madrid EQ to the 1906 San Francisco EQ.

  25. GEOLOGY-Earthquakes • Mercalli Impact-Columbia is in V.

  26. GEOLOGY-Earthquakes • 12,000,000 people live in EQ zone-St. Louis, Memphis, Evansville, Louisville, Cape Girardeau • Same quake today could kill 100,000 and trillions of dollars of damage • PROBLEM-Minor quakes relieve pressure and prevent larger quakes. We need minor quakes!

  27. GEOLOGY-Earthquakes LINKS TO DAILY EARTHQUAKE REPORTS http://www.weather.com/images/maps/special/usa_earth_720x486.jpg http://neic.usgs.gov/neis/qed/

  28. GEOLOGY-Earthquakes-Wrap ups • 1. Define an Earthquake • 2. What are the Focus and Epicenter? • 3. How is the epicenter determined? • 4. What is the Richter scale and what does it measure? • 5. What is the Mercalli scale and what does it measure?

  29. GEOLOGY-Earthquakes-Wrap ups • 6. What are the characteristics of the 1906 San Francisco EQ? • 7. What are the characteristics of the 1964 Alaska EQ? • 8. What are the characteristics of the 1811-1812 New Madrid EQ? • 9. What are the chances for a major EQ in MO? • 10. Why should be be concerned everyday there is not a major EQ in New Madrid?

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