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U.S. Department of the Interior U.S. Geological Survey

The Earthquake is Inevitable: The Disaster is Not. U.S. Department of the Interior U.S. Geological Survey. Earthquake Organizations. U.S. Geological Survey Federal agency in Department of Interior Caltech Seismological Laboratory Private university Southern California Earthquake Center

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U.S. Department of the Interior U.S. Geological Survey

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  1. The Earthquake is Inevitable:The Disaster is Not U.S. Department of the Interior U.S. Geological Survey

  2. Earthquake Organizations • U.S. Geological Survey • Federal agency in Department of Interior • Caltech Seismological Laboratory • Private university • Southern California Earthquake Center • Consortium of universities & USGS • California Geological Survey • State agency in Department of Conservation • Office of Emergency Services • State agency in Homeland Security

  3. Today’s speakers • Lucy Jones, USGS • Scientist-in-charge for southern California • Gary Fuis, USGS • Project chief, Southern California Earthquake Hazards • Egill Hauksson, Caltech • Senior Research Associate • Ken Hudnut, USGS • Project chief, Southern California Earthquake Hazards • Tom Jordan, SCEC • Director, Southern California Earthquake Center

  4. The Earthquake is Inevitable:The Disaster is Not U.S. Department of the Interior U.S. Geological Survey

  5. What is an earthquake?

  6. What is an Earthquake? • Sudden slip of one block of rock across another • Produces shaking as one of its effects • The shaking is what you feel

  7. Magnitude • Empirical and arbitrary • Defined from ground velocity • Each unit means 32 times more energy M5 M6 M7

  8. Moment Magnitude • Depends on: • Fault area • Amount of slip • Each unit means 32 times more energy M5 M6 M7

  9. Every point on the rupture surface releases energy Rupture Surface Hypocenter Faultplane A bigger fault means a bigger earthquake Fault Epi- center Hypo-center

  10. Bigger Faults Make Bigger Earthquakes

  11. Shaking = damage potential ShakeMap M4.8 Yorba Linda September 2002

  12. What Controls the Level of Shaking? • Magnitude • More energy released

  13. What Controls the Level of Shaking? • Magnitude • More energy released • Distance • Shaking decays with distance

  14. Hector Mine October 16, 1999 M7.1 Northridge January 17, 1994 M6.7

  15. What Controls the Level of Shaking? • Magnitude • More energy released • Distance • Shaking decays with distance • Local soils • amplify the shaking

  16. Undamaged Buildings on the fault 1906 San Francisco

  17. Damage at Great Distance The Bay Bridge 1989 Loma Prieta The Marina District

  18. SiteEffects

  19. Big earthquakes on big faults • M7.9 Denali, Alaska • November 3, 2002 • 200+ mile long fault

  20. Near people…

  21. Magnitude = Time • Earthquakes start at hypocenter • The rupture moves over a surface • Duration of earthquake depends on magnitude

  22. Distance along the fault plane, 100 km (60 miles) total length Total Slip in the M7.3 Landers Earthquake

  23. Surface of the earth Depth e into the earth Distance along the fault plane, 100 km (60 miles) total length Slip on an earthquake fault: Start

  24. Slip on an earthquake fault: Second 2.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  25. Slip on an earthquake fault: Second 4.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  26. Slip on an earthquake fault: Second 6.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  27. Slip on an earthquake fault: Second 8.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  28. Slip on an earthquake fault: Second 10.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  29. Slip on an earthquake fault: Second 12.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  30. Slip on an earthquake fault: Second 14.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  31. Slip on an earthquake fault: Second 16.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  32. Slip on an earthquake fault: Second 18.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  33. Slip on an earthquake fault: Second 20.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  34. Slip on an earthquake fault: Second 22.0 Surface of the earth Depth into the earth Distance along the fault plane, 100 km (60 miles) total length

  35. Slip on an earthquake fault: Second 24.0 Surface of the earth Depth Distance along the fault plane, 100 km (60 miles) total length

  36. Bigger Earthquakes Last a Longer Time

  37. The Risk in Southern California • 300+ faults • One M≥6.7 event per 7 years

  38. The Big Bend Los Angeles has the greatest risk in the United States

  39. The bottom line: Earthquakes happen National hazards map Courtesy of California Geological Survey & U. S. Geological Survey

  40. Scenario ShakeMap for M 7.4 Southern San Andreas Rupture Courtesy of Ned Field, USGS, Pasadena

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