J. Louie 4/15/04J. Louie 4/15/04

Louie, J. N.Louie, J. N.Scott, J. B.Scott, J. B.

Rasmussen, T.Rasmussen, T.Thelen, W. A.Thelen, W. A.

Pancha, A.Pancha, A.Clark, M.Clark, M.Park, H.Park, H.

Lopez, C. T. Lopez, C. T.

www.seismo.www.seismo.unr.edu/unr.edu/hazsurvhazsurv

Shallow Shear-Velocity Transects of Urban Shallow Shear-Velocity Transects of Urban Areas, and Seismic-Hazard MappingAreas, and Seismic-Hazard Mapping

J. Louie 4/15/04J. Louie 4/15/04

Transect Results Partly Explain PGATransect Results Partly Explain PGA

Soil Classes?Soil Classes?

Weak Soils?Weak Soils?

Supported by USGS-NEHRP Supported by USGS-NEHRP and IRIS-PASSCALand IRIS-PASSCAL

J. Louie 4/15/04J. Louie 4/15/04

Three Transects Show Geologic VariationsThree Transects Show Geologic Variations

J. Louie 4/15/04J. Louie 4/15/04

Statistics of Geologic VariationStatistics of Geologic Variation Linear slope in log-log spatial spectrumLinear slope in log-log spatial spectrum

Fractal variations are probably geologicalFractal variations are probably geological Levels out at endLevels out at end

Some variance across <0.6 km is experiment errorSome variance across <0.6 km is experiment error

J. Louie 4/15/04J. Louie 4/15/04

VV3030 vs Soil Type vs Soil Type

Large standard deviations with good averagesLarge standard deviations with good averages Units 3 and 4 well-sampled over long distancesUnits 3 and 4 well-sampled over long distances

J. Louie 4/15/04J. Louie 4/15/04

VV3030 vs Soil Type vs Soil Type

Standard deviations increase with sample sizeStandard deviations increase with sample size Average velocities of units change along transectAverage velocities of units change along transect

J. Louie 4/15/04J. Louie 4/15/04

Supported by DOE-LLNL Supported by DOE-LLNL and IRIS-PASSCALand IRIS-PASSCAL

Las Vegas TransectLas Vegas Transect

J. Louie 4/15/04J. Louie 4/15/04

Field’s (2001) Amplification MappingField’s (2001) Amplification Mapping

Needs only basin depth and Vs30Needs only basin depth and Vs30 Trial maps made using coefficients from LATrial maps made using coefficients from LA

Field’s (2001) Amplification MappingField’s (2001) Amplification Mapping

Field; Wald & Mori (2000)Field; Wald & Mori (2000)

BNEHRP-D C

J. Louie 4/15/04J. Louie 4/15/04

Extrapolating Vs30: Las VegasExtrapolating Vs30: Las Vegas Vs30 assigned to soil-map units using transectVs30 assigned to soil-map units using transect Maps don’t predict new measurements- B. Luke, UNLVMaps don’t predict new measurements- B. Luke, UNLV

J. Louie 4/15/04J. Louie 4/15/04

SummarySummary

300 sites on 3 urban transects measured 300 sites on 3 urban transects measured

for Vs30.for Vs30.

Vs30 may partly explain PGA, hazard Vs30 may partly explain PGA, hazard

variations.variations.

Long transects show fractal, geologic Long transects show fractal, geologic

variations in Vs30.variations in Vs30.

Geologic, soil maps do not have sufficient Geologic, soil maps do not have sufficient

Vs30 predictive value for engineering.Vs30 predictive value for engineering.