J. Louie 9/5/2005J. Louie 9/5/2005

OutlineOutlineOutlineOutline

1.1. Refraction Microtremor for Shallow VsRefraction Microtremor for Shallow Vs

2.2. ReMi-Borehole ComparisonReMi-Borehole Comparison

3.3. Los Angeles TransectLos Angeles Transect

4.4. Las Vegas TransectLas Vegas Transect

5.5. Effect of Shallow Vs on Shaking ModelsEffect of Shallow Vs on Shaking Models

1.1. Refraction Microtremor for Shallow VsRefraction Microtremor for Shallow Vs

2.2. ReMi-Borehole ComparisonReMi-Borehole Comparison

3.3. Los Angeles TransectLos Angeles Transect

4.4. Las Vegas TransectLas Vegas Transect

5.5. Effect of Shallow Vs on Shaking ModelsEffect of Shallow Vs on Shaking Models

J. Louie 9/5/2005J. Louie 9/5/2005

Building a Las Vegas Seismic ModelBuilding a Las Vegas Seismic ModelBuilding a Las Vegas Seismic ModelBuilding a Las Vegas Seismic Model

J. Louie 9/5/2005J. Louie 9/5/2005

Model Rendered as Amplification MapModel Rendered as Amplification Map Geology, Basin Depth, Geotech, Geophysical data into Geology, Basin Depth, Geotech, Geophysical data into ModelAssemblerModelAssembler

Las VegasBasinLas VegasBasin

LittleSkull Mtn.LittleSkull Mtn.

DeepVolcanicRifts

DeepVolcanicRifts

J. Louie 9/5/2005J. Louie 9/5/2005

Max. Ground Motion Computed– 0.1 HzMax. Ground Motion Computed– 0.1 Hz E3D elastic finite-difference solution, by Shawn Larsen, LLNLE3D elastic finite-difference solution, by Shawn Larsen, LLNL

Las VegasBasinLas VegasBasin

LittleSkull Mtn.LittleSkull Mtn.

DeepVolcanicRifts

DeepVolcanicRifts

J. Louie 9/5/2005J. Louie 9/5/2005

Detailed Model Makes a Difference- even at 0.1 HzDetailed Model Makes a Difference- even at 0.1 Hz Max. ground motion ratio, models with and without geotechnical modelMax. ground motion ratio, models with and without geotechnical model

LittleSkull Mtn.

Las VegasBasinLas VegasBasin

J. Louie 9/5/2005J. Louie 9/5/2005

Detailed Model Makes a DifferenceDetailed Model Makes a Difference But not in any way that can be predicted from the model alone– basin But not in any way that can be predicted from the model alone– basin

geometry, source, and propagation path all matter!geometry, source, and propagation path all matter!

73% predicted for 2-4 Hz73% predicted for 2-4 Hz 6% computed for 0.1 Hz6% computed for 0.1 Hz

J. Louie 9/5/2005J. Louie 9/5/2005

Max. Ground Motion Computed– 0.5 HzMax. Ground Motion Computed– 0.5 Hz E3D elastic finite-difference solution, by Shawn Larsen, LLNLE3D elastic finite-difference solution, by Shawn Larsen, LLNL

Las VegasBasinLas VegasBasin

LittleSkull Mtn.Little

Skull Mtn.

DeepVolcanicRifts

DeepVolcanicRifts

J. Louie 9/5/2005J. Louie 9/5/2005

Comparing Computed GM at 0.5 HzComparing Computed GM at 0.5 Hz At UNLV in the southern part of LVV, there are unexpected waveform At UNLV in the southern part of LVV, there are unexpected waveform

differences, even with the similar maximum motions.differences, even with the similar maximum motions.

J. Louie 9/5/2005J. Louie 9/5/2005

Comparing Computed GM at 0.5 HzComparing Computed GM at 0.5 Hz In central Las Vegas Valley, the detailed model has lower velocities In central Las Vegas Valley, the detailed model has lower velocities

(0.35 km/s) than the 0.5 km/s Vs30 assumed for basins.(0.35 km/s) than the 0.5 km/s Vs30 assumed for basins.

Detailed LVV ModelDetailed LVV Model Basin Vs30=0.5 km/s ConstantBasin Vs30=0.5 km/s Constant

J. Louie 9/5/2005J. Louie 9/5/2005

Detailed Model Makes a Difference at 0.5 HzDetailed Model Makes a Difference at 0.5 Hz Max. ground motion ratio, models with and without geotechnical modelMax. ground motion ratio, models with and without geotechnical model

LittleSkull Mtn.

Las VegasBasinLas VegasBasin

J. Louie 9/5/2005J. Louie 9/5/2005

Detailed Model Makes a Difference- at 0.5 HzDetailed Model Makes a Difference- at 0.5 Hz In a way that can be partly predicted from the model alone– but basin In a way that can be partly predicted from the model alone– but basin

geometry, source, and propagation path still matter at 0.5 Hz.geometry, source, and propagation path still matter at 0.5 Hz.

73% predicted for 2-4 Hz73% predicted for 2-4 HzUp to 213% computed for 0.5 HzUp to 213% computed for 0.5 Hz

J. Louie 9/5/2005J. Louie 9/5/2005

Conclusions IIConclusions IIConclusions IIConclusions II

In tectonic areas, the regional In tectonic areas, the regional

distribution of distribution of basinsbasins affects shaking. affects shaking.

We have built a We have built a ModelAssemblerModelAssembler for for

Nevada to create 3-d computation grids Nevada to create 3-d computation grids

from geological and geotechnical data.from geological and geotechnical data.

Surprisingly, geotechnical Surprisingly, geotechnical detailsdetails affect affect

even 10-sec computations in ways even 10-sec computations in ways

difficult to forecast.difficult to forecast.

In tectonic areas, the regional In tectonic areas, the regional

distribution of distribution of basinsbasins affects shaking. affects shaking.

We have built a We have built a ModelAssemblerModelAssembler for for

Nevada to create 3-d computation grids Nevada to create 3-d computation grids

from geological and geotechnical data.from geological and geotechnical data.

Surprisingly, geotechnical Surprisingly, geotechnical detailsdetails affect affect

even 10-sec computations in ways even 10-sec computations in ways

difficult to forecast.difficult to forecast.