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?