The document summarizes the findings of a 2005 report that evaluated the expected performance of buildings and infrastructure in the Pacific Northwest region in the event of a major earthquake on the Seattle Fault. The report estimated that around 4,000 commercial structures, particularly unreinforced masonry buildings, older reinforced concrete tilt-ups, and pre-1970 reinforced concrete frames built on poor soil, would experience significant damage. It also projected that over 46,000 households would be displaced. The scenario earthquakes would cause significantly stronger ground motions than recent quakes in the region. While modern structures may survive with some damage, many older buildings could experience significant damage or collapse.

1. Earthquakes in Cascadia—
Performance of the Built Environment
of the Built Environment
John Hooper, P.E., S.E.
February 13, 2013

2. Earthquake Sources in PNW

4.  Minimum acceptable lateral strength and stiffness
 Minimum acceptable detailing practices
 Required attachment strength and displacement
capacity of nonstructural components
 Design Intent: Low likelihood of collapse given the
MCE

6. 1970

7. 1976

8. 1994
3
4

16. Soil Liquefaction Zone—Seattle

17. Seattle Fault Scenario
 Published June 2005 by:
 Earthquake Engineering Research Institute
(EERI)
 Washington Military Department—
Emergency Management Division
 Evaluated performance of:
 Lifelines
 Transportation
 Essential Facilities
 Buildings

19. Local Building Stock

20. Local Building Stock

21. Local Building Stock

22. Local Building Stock

23. EQ Performance Factors
 Year design/built (year and code)
 Type of system (shear wall, moment frame,
braced frame)
 Primary material (steel, concrete, masonry,
wood)
 Type of soil (soft soil vs. stiff soil)
 Building layout
 Geometry (rectangular, L-shaped)
 Openings above grade
 Quality of design and construction

24. Scenario Damage Estimates
 Very strong ground motions near the fault
 4,000 (27%) commercial structures with significant
damage:
 Unreinforced masonry (URMs)
 Reinforced concrete tilt-ups
 Pre 1970-vintange reinforced concrete frame
systems
 Significant damage to structures on poor soil
 46,000+ households displaced
 Long-term impact on industry and economy

26. URMs

27. Retrofitted URM

28. Older Tilt-up Buildings

29. Older Reinforced Concrete Frame

30. Seattle Fault Scenario Conclusions
 Scenario ground motions are significantly
greater than those in recent local earthquakes
 Modern structures would survive with varying
degrees of damage
 Many older structures would experience
significant damage with some collapses

31. Questions??