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Safety of Dams Flood and Earthquake Criteria (1985) / Chapter Skim
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Proposed Earthquake Criteria
Pages 106-109

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From page 106...
... Earthquake experience along some major fault systems suggests shorter average return periods. It seems clear that the earthquakes adopted for safety evaluations do not represent as rare phenomena as do probable maximum precipitation estimates, which are generally considered to represent rainfalls having average return periods of from 10,000 years to as long as 1,000,000 years.
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From page 107...
... However, since both types of estimates represent probable maximum events, these differences in probabilities do not represent inconsistent approaches. DESIGN CRITERIA The committee suggests that the federal agencies adopt the terminology "safety evaluation earthquake" (SEE)
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From page 108...
... Embankment Dams · In design and construction, adopt such "defensive measures" as ample freeboard, wide transition zones, adequate compaction of materials in foundations and embankment, and a high level of quality control. · For reasonably well-built dams on stable soil or rock foundations, the pseudostatic method of stability analysis may be used if estimated peak ground accelerations are less than 0.2 g.
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From page 109...
... COMBINED EARTHQUAKE AND FLOOD CRITERIA The committee does not consider it necessary to design dams to withstand the simultaneous occurrence of the safety evaluation earthquake and the safety evaluation flood. However, if an existing spillway is subject to frequent use, and an analysis with an OBE indicates that the spillway may be so damaged as to be unusable, the safety of the dam should be considered unsatisfactory.
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Key Terms

  • evaluation earthquake
  • average return
  • safety evaluations
  • earthquake criteria
  • return periods

  • ground motion
  • ground accelerations
  • probable maximum
  • evaluation flood
  • earthquake ground

  • dam safety
  • peak ground
  • earthquakes adopted
  • committee endorses
  • earthquake safety

  • dynamic response
  • motions considered
  • earthquake experience
  • estimated peak
  • committee suggests

  • represent inconsistent
  • significant probability
  • method applied
  • seismic design
  • pseudostatic method

  • dams located
  • major fault
  • rapidly affect
  • assumed level
  • extreme floods


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