1 / 38

Intraplate Earthquakes

Intraplate Earthquakes. New Madrid, Missouri : December 1811, January 1812, February 1812 . Intraplate Earthquakes. Eastern U.S. earthquakes less frequent, but more widely felt Crust is older and transmits stress. Earthquake Size and Characteristics. How big is it?

luce
Télécharger la présentation

Intraplate Earthquakes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Intraplate Earthquakes • New Madrid, Missouri: December 1811, January 1812, February 1812

  2. Intraplate Earthquakes • Eastern U.S. earthquakes less frequent, but more widely felt • Crust is older and transmits stress

  3. Earthquake Size and Characteristics • How big is it? • Answer in terms of perceived effects: intensity • Answer in terms of amount of energy released: magnitude

  4. Earthquake Intensity • Mercalli Intensity Scale developed in 1902 • Based on effects • Local small quake is similar to distant large quake

  5. Felt effects using Mercalli Scale http://www.scec.org/instanet/01news/images/NorthridgeSMap.gif

  6. Felt effects using Mercalli Scale Hypothetical M7.8 earthquake

  7. Landers 1992 earthquake: Felt intensity by zip code

  8. Earthquake Magnitude • Richter Magnitude Scale (ML) derived by Charles Richter in 1935 • Uses maximum amplitude of earthquake waves on seismograph • Logarithmic scale • Richter magnitude less accurate above M6.5

  9. Problems with scales • Moment magnitude is measure of total energy expended during earthquake • Determined from long-period waves • Moment = (shear strength of rocks) x (surface area of rupture) x (slip distance on fault) • Each number is 32X energy • Each 2 numbers =1000X • This is the most common scale for quakes >3.5

  10. Another example of M=1/f

  11. 1995 Kobe earthquake, Japan

  12. 1989 Loma Prieta earthquake, SF Bay Area

  13. Liquifaction Water in sediment causes solid rock to behave like a liquid.

  14. Liquifaction

  15. Secondary Ground Effects • Surface rupture-scarp • Earthquakes often trigger landslides • Can also cause liquefaction • Soils become almost liquid when shaken, solidify when shaking stops • Significant damage to structures atop liquefied sediments • Fires

  16. Surface rupture-scarp

  17. 1906 earthquake surface rupture. 8’ fence offset above http://mnw.eas.slu.edu/Earthquake_Center/1906EQ/1906thumb.html And http://quake.wr.usgs.gov/info/1906/images/fenceoffset_big.html

  18. Australia, 1968, M6.8

  19. Armenia, 1988, M6.9

  20. Borah Peak, ID: 1983 M7.3

  21. California, 1979, M6.9

  22. Landslides caused by 2002 Denali Fault earthquake

  23. 1965 Seattle quake M6.5

  24. Liquifaction Water in sediment causes solid rock to behave like a liquid.

  25. This residential and commercial building sank more than three feet into the partially liquefied soil.

  26. Liquifaction: Niigata, Japan, 1964 :

  27. San Francisco 1906 M8.3 Secondary effects: Fire

  28. Long term probability • Probability of where and when an earthquake will strike used to construct risk map

  29. Earthquake Hazards2% chance in next 50 years

  30. The San Francisco Bay Area

  31. Las Cruces: 15-18% chance of M5 in 50 yrs.

  32. Sample Test Questions

More Related