Probabilistic Seismic Hazard Maps Inputs and Status

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Probabilistic Seismic Hazard Maps - Inputs and
Status

• Choi Yoon Seok
• Jennifer S. Haase
• Robert L. Nowack
• Purdue University

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Status

• Preliminary data sets used as of 11/20/05
• Approximate bedrock topography and surface wave
  velocity model constructed.
• Preliminary v1.0 full calculation completed and
  presented at Fall AGU 12/8/05
• Very sensitive to bedrock depth
• Second calculation using new version of Cramers
  PSHA code completed 2/18/06
• 0.2 sec expected acc. Increased by 0.1g
• Investigated larger period range
• Third run with finalized model planned 4/06

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Amplification Factor
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Amplification Factor
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PSHA maps
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Data inputs

• 48 USGS CPT
• Used to assign Vs to unit types - loess,
  alluvium, lacustrine - averaged over depth to one
  Vs
• 33 borehole Vs
• Used to assign Vs to unit types - averaged over
  depth to one Vs
• 570 new SPT at 60 geotechnical sites
• Not used - not satisfied with SPT gt Vs
• 230 Vp refraction
• Used for depth to bedrock
• Used for bedrock velocity (VsVp/1.72)

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Data inputs

• KGS Vs refraction profiles (CUSEC report)
• Used only to check approx bedrock Vs
• IGS Ilith water well logs
• Used for bedrock depth
• Not used for densifying lateral varying
  lithology, yet
• KY bedrock elevation points (R. Counts)

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Data inputs

• Surficial geology
• Used to determine surface lithology type, then
  one velocity and uncertainty assigned to all grid
  points within that map area
• All these surficial geology maps were preliminary
  products

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Quadrangle Map Status?
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Bedrock depth model
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Effect of depth of soil on amplification

• At 0.05 g input

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Whats left to try?

• Use more data to determine correspondence between
  velocity and unit lithology
• Water wells and SPTs calculate average velocity
  given the total thickness of different units
  using lithology for each unit
• Try a depth dependence for each unit
• Need some kind of numbers for bedrock
• Refraction data in Rons marginal areas
• Make cross sections through our Vs/bedrock model
  for detailed cross section lines to make sure
  they are consistent with detailed depositional
  cross sections.

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Products

• PSHA maps at any level desired
• Level of acceleration in g with X probability to
  be exceeded in 50 years
• At pga, 0.2 sec, 1 sec (or others)
• 9 quadrangle region
• Scenario earthquake calculation for Indiana side?
  Using same scenarios as Zhenming?

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Products

• From 3D Vs above bedrock model can calculate
  site classification
• Give information to CUSEC to make updated NEHRP
  soil classification maps
• These could be available products to other
  scientists and also users of HAZUS