Earthquake hazards - PowerPoint PPT Presentation

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Earthquake hazards

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  1. Earthquake hazards • Ground Rupture Alaskan pipe after the Denali quake ruptured through Ground rupture from the M8.1 2001 Tibet earthquake

  2. Earthquake hazards (cont.) • Shaking • Wave amplitude • Wave frequency • Duration of shaking

  3. 1964 Nigata Japan 2004 Sumatra earthquake Earthquake hazards (cont) • Liquefaction • Saturated sand loses strength upon shaking • Tsunami • Wave wavelength ocean waves that can travel vast distances

  4. Sumatra Earthquake tsunami

  5. Seismic Hazard of MA

  6. Cape Ann Earthquake 1755 Woodcut illustration depicting damage in Boston from the earthquake

  7. Hazard vs risk • 1989 Macquarie Ridge, New Zealand • M 8.3 • No losses • 1960 Agadir, Morocco • M 5.5 • 12,000 deaths

  8. Earthquake Risk • Risk = hazard x vulnerability • The amount of damage and numbers of earthquake related deaths do not correlate to magnitude of the earthquake.

  9. Products of hazard assessment • Active fault map • Historical seismicity • Earthquake likelihood

  10. 3D models assess seismic hazard in Los Angeles, CA SCEC Community Fault Model

  11. Acceptable Risk • Level of acceptable risk depends on the structure • Cannot design for maximum earthquake with low probability • Social question

  12. How would you mitigate damages from…. • Ground Rupture • Liquefaction • Ground Shaking • Tsunami

  13. Ground Rupture • Avoid construction • Relocate sensitive facilities • Implement low use facilities • Playing fields • Green space

  14. Portola Valley California

  15. Liquefaction • Recognize liquefaction potential • In-situ remediation • Avoid construction in liquefaction prone areas

  16. Tsunami mitigation • Early warning system • Broadcast signal to beaches after a major earthquake anywhere in the ocean basin • Saftey guidelines • Go to high ground • Climb a tree

  17. Ground Shaking • Recognize the degree of probable ground shaking in the area • Improve construction methods to accommodate shaking without collapse