Ground Motion Maps 5b - 1Instructional Materials Complementing FEMA 451, Design Examples
GROUND MOTION MAPSHow To Obtain the Basic Values
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Seismic Ground Motions
1 Determine basic values from maps for bedrock conditions
2, 3 Classify soil conditions at site and determine site coefficients
4 Determine site-adjusted values4 Take two-thirds for use in design5 Construct design response spectrum7 Site-specific studies permitted/required
Ground Motion Maps 5b - 3Instructional Materials Complementing FEMA 451, Design Examples
Mapped Acceleration Parameters
• Two sets of maps; acceleration parameter is in units of gravity
• SS for spectral response acceleration at 0.2 sec• S1 for spectral response acceleration at 1.0 sec• Shortcut to Seismic Design Category A:
SS < 0.15 and S1 < 0.04
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SS and S1 are themapped 2% in 50 yearspectral accelerationsfor firm rock
SDS and SD1 are thedesign level spectralaccelerations (modifiedfor site and “expectedgood performance”)
Ground Motion Parameters & Seismic Hazard
Mapped Contours of SS
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Long-Period Transition Maps
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Location of Deterministic Areas
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Typical Probabilistic Map
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CD vs Internet
• Internet• CD• Both sources give the same answers• Both sources have a similar user
interface• The graphics are somewhat different
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Internet Ground Motion Tool
http://earthquake.usgs.gov/research/hazmaps/
SEISMIC DESIGN VALUES FOR BUILDINGS
Ss and S1, Hazard Curves, Uniform Hazard Spectra, and Residential Design Category
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USGS Ground Motion Calculator
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Installation
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Installation Caution
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Opening Screen
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Analysis Options
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IBC Option
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User Aids
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Calculate SS AND S1
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Location By Zipcode
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Calculate SMS, SM1, SDS, SD1
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Calculate Site Coefficients
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SMS, SM1, SDS, SD1 Values
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Calculate MCE Spectrum
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Calculate SM Spectrum
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Calculate SD Spectrum
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Graphic Options
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Map Spectrum: Sa - T
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All Spectra: Sa - T
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Calculate Hazard Curves
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Annual Frequency of Exceedance
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Return Period
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Single Values
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Deaggregation
• Breaking apart of the probabilistic hazard analysis
• Helps remove some of the “black box”effect
• Helps visualize the source of the hazard
• Many uses, e.g. liquefaction analysis, time history determination
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Deaggregation – San Francisco
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Deaggregation - Coos Bay, Oregon
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Deaggregation - Portland, Oregon
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Deaggregation – Olympia, Washington
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Seattle – 0.2 sec, Detailed
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Seattle – 0.2 sec
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Seattle – 1.0 sec
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Design Values Outside the United States
• Based on GASHAP Data• 10% PE in 50 years• PGA only• Estimate 2% from 10% PE by multiplying by
2.0• Ss = 2.5xPGA• S1 = PGA• Use site-specific studies where available• USGS studies where available
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UFC 3-310-1
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What is GSHAP?