Seismic Shaking in Nevada’s Urban Areas: Computing Simple Scenarios

J. Louie, UNR 2/7/2007J. Louie, UNR 2/7/2007

Seismic Shaking inSeismic Shaking inNevada’s Urban Areas:Nevada’s Urban Areas:

Computing Simple ScenariosComputing Simple Scenarios

John Louie, 2/7/07John Louie, 2/7/07

Fall 2006 Geol 455 students:Fall 2006 Geol 455 students: Liz Lenox Liz Lenox Rei AraiRei Arai Amr WakwakAmr Wakwak


A code to stitch A code to stitch together existing together existing regional regional geophysical and geophysical and geological data geological data sets.sets.

Generates multi-Generates multi-gigabyte E3D gigabyte E3D input grids.input grids.

ModelModelAssemblerAssembler


The ModelAssembler Community The ModelAssembler Community Modeling Environment (MA-CME)Modeling Environment (MA-CME)

Graphical user interface for setting up MA/E3D “.in” files.Graphical user interface for setting up MA/E3D “.in” files. Provides tutorial help to successful setup.Provides tutorial help to successful setup. Data sets, stations, grids all defined with geographic Data sets, stations, grids all defined with geographic

lat/lon lat/lon (have to decide on WGS84, NAD27, etc.).(have to decide on WGS84, NAD27, etc.).

Easy configuration of problems at all scales and Easy configuration of problems at all scales and computational difficulties- 10 Mb to 100 Gb.computational difficulties- 10 Mb to 100 Gb.

After setup, “portal pack” is downloaded to cluster and After setup, “portal pack” is downloaded to cluster and run.run.

Open source: Open source: www.seismo.unr.edu/mawww.seismo.unr.edu/ma Limits:Limits: flat earth; no topography; 1-D variations within flat earth; no topography; 1-D variations within

basins & bedrock; source and stations in same grid.basins & bedrock; source and stations in same grid.


Define Execution PlatformDefine Execution Platform


Set up GridSet up Grid


Define Earthquake SourceDefine Earthquake Source


Define Rule BaseDefine Rule Base


Arrange Basin-Thickness (& Geotech) InputsArrange Basin-Thickness (& Geotech) Inputs


Request Output DataRequest Output Data


Frenchman Mountain FaultFrenchman Mountain Fault

4x4-km N-striking M5.0 scenario4x4-km N-striking M5.0 scenario West-dipping oblique-normalWest-dipping oblique-normal Late Quaternary (<130 ka)Late Quaternary (<130 ka) Less than 0.2 mm/yrLess than 0.2 mm/yr By Amr Wakwak (Fulbright PLUS Program)By Amr Wakwak (Fulbright PLUS Program)



Scott et al. (2006) Scott et al. (2006) Vs30 model from Vs30 model from 1100+ wells, 79 1100+ wells, 79 Vs profiles. Vs profiles.

Thanks to W. Thanks to W. Taylor of UNLV & Taylor of UNLV & G. Wagoner of G. Wagoner of LLNLLLNL



Langenheim et Langenheim et al. model from al. model from gravity, gravity, refraction, a few refraction, a few deep wells.deep wells.



Animation combines Animation combines inputs and outputs.inputs and outputs.

E3D computation at E3D computation at 0.3 Hz on a 0.3 Hz on a 144x137 grid with 144x137 grid with dh=308 m.dh=308 m.

Grid resolution is a Grid resolution is a good match to cell good match to cell phone displays.phone displays.

QuickTime™ and aVideo decompressor

are needed to see this picture.



PGV >5 cm/s PGV >5 cm/s above west-above west-dipping fault at dipping fault at 0.3 Hz.0.3 Hz.

Sub-basins Sub-basins contain the contain the greatest shaking.greatest shaking.


Frenchman Mountain FaultFrenchman Mountain FaultSchools closest to the fault experience greatest PGV but shortest Schools closest to the fault experience greatest PGV but shortest durations.durations.


Genoa Fault – Genoa Fault – Mount Rose Mount Rose

Fault SystemsFault Systems 80 km long80 km long East-dipping East-dipping

oblique-normaloblique-normal Latest Quaternary Latest Quaternary

(<15 ka)(<15 ka) 1.0-5.0 mm/yr1.0-5.0 mm/yr Northward rupture Northward rupture

scenario from W. scenario from W. Fork Carson Riv. to Fork Carson Riv. to Virginia LakeVirginia Lake

By Rei AraiBy Rei AraiW. Fork Carson Riv.W. Fork Carson Riv.

Virginia LakeVirginia Lake


Genoa Fault – Genoa Fault – Mount Rose Mount Rose

Fault SystemsFault SystemsScott et al. (2004) Vs30 Scott et al. (2004) Vs30 transect.transect.

Pancha measurements at Pancha measurements at ANSS stations. ANSS stations.

““Quadrant” interpolation Quadrant” interpolation between scattered between scattered measurements, respecting measurements, respecting geologic map.geologic map.

Vs30=500 m/s assumed Vs30=500 m/s assumed on sediment, 760 m/s on sediment, 760 m/s (white and cyan) on rock.(white and cyan) on rock.


Genoa Fault – Genoa Fault – Mount Rose Fault Mount Rose Fault

SystemsSystems

Three datasets, not well Three datasets, not well stitched together:stitched together:

1)1) Geologic map with basin Geologic map with basin depths assumed from bedrock depths assumed from bedrock proximity, in California.proximity, in California.

2)2) Jachens et al. USGS basin Jachens et al. USGS basin gravity inversions for Basin & gravity inversions for Basin & Range; sedimentary plus Range; sedimentary plus Tertiary volcanic basins.Tertiary volcanic basins.

3)3) Abbott & Louie (2000) Reno Abbott & Louie (2000) Reno basin gravity study.basin gravity study.


Genoa Fault – Mount Rose Fault SystemsGenoa Fault – Mount Rose Fault Systems

Dataset mismatches Dataset mismatches plain in model plain in model renderings.renderings.

Extreme directivity Extreme directivity effect.effect.

E3D computation at E3D computation at 0.3 Hz on a 0.3 Hz on a 120x200 grid with 120x200 grid with dh=500 m.dh=500 m.

Olsen and Day Q Olsen and Day Q model included.model included.

QuickTime™ and aPhoto - JPEG decompressor



Genoa Fault – Genoa Fault – Mount Rose Fault Mount Rose Fault

SystemsSystems

West Reno basin, above end of West Reno basin, above end of rupture, has 5x the PGV of any rupture, has 5x the PGV of any other basin near fault.other basin near fault.

Highest shaking not correlated Highest shaking not correlated with basin depth- Tahoe with basin depth- Tahoe artificially deep in this model.artificially deep in this model.

Dataset boundaries not Dataset boundaries not interfering with these interfering with these conclusions.conclusions.


Genoa Fault – Mount Rose Fault SystemsGenoa Fault – Mount Rose Fault SystemsWest Reno stations have high PGV and long durations.West Reno stations have high PGV and long durations.


Northern Death Valley Fault ZoneNorthern Death Valley Fault Zone

80 km long80 km long Dextral strike-slipDextral strike-slip 1.0- 5.0 mm/yr1.0- 5.0 mm/yr Latest Quaternary (<15 ka)Latest Quaternary (<15 ka) Two M7.5 scenarios:Two M7.5 scenarios:

Rupture from SE, epicenter at Furnace Crk.Rupture from SE, epicenter at Furnace Crk. Rupture from NW, epicenter at Ubehebe Ctr.Rupture from NW, epicenter at Ubehebe Ctr.

By Liz LenoxBy Liz Lenox

Ubehebe Crater

Furnace Creek



Jachens USGS Jachens USGS geologic map geologic map sets default soil sets default soil and rock Vs30s.and rock Vs30s.

Scott et al. Scott et al. (2006) Vs30 (2006) Vs30 model from model from 1100+ wells, 79 1100+ wells, 79 Vs profiles Vs profiles inserted for inserted for LVV. LVV.



Jachens Basin Jachens Basin & Range gravity & Range gravity inversions for inversions for sedimentary & sedimentary & volcanic basins.volcanic basins.

Timber Mtn. Timber Mtn. caldera & rifts caldera & rifts up to 8 km up to 8 km deep. deep.

Langenheim et Langenheim et al. model from al. model from gravity, gravity, refraction, a few refraction, a few deep wells deep wells inserted for inserted for LVV.LVV.



Animation combines Animation combines inputs and outputs.inputs and outputs.

E3D computation at E3D computation at 0.3 Hz on a 0.3 Hz on a 281x251 grid with 281x251 grid with dh=1 km.dh=1 km.

Infinite Q.Infinite Q.

The two rupture The two rupture scenarios have very scenarios have very different effects.different effects.

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For rupture For rupture away from city, away from city, PGV <<1 cm/s PGV <<1 cm/s in LVV.in LVV.

Clear directivity Clear directivity in this long-in this long-period period simulation.simulation.



For rupture For rupture toward city, toward city, PGV >1 cm/s in PGV >1 cm/s in LVV.LVV.

Clear directivity Clear directivity in this long-in this long-period period simulation.simulation.

Basins between Basins between DV and LVV are DV and LVV are spreading the spreading the directivity effect directivity effect to wider angles to wider angles from the fault from the fault strike.strike.



Ratio of PGV Ratio of PGV from rupture from rupture toward LVV, toward LVV, over away.over away.

Largest Largest amplifications amplifications due to directivity due to directivity are in bedrock.are in bedrock.

Some margins Some margins of LVV also of LVV also show 1500% show 1500% amplifications.amplifications.


Northern Death Valley Fault ZoneNorthern Death Valley Fault ZoneCompare PGV of 2679 areas, each 1-kmCompare PGV of 2679 areas, each 1-km22, in LVV against Vs30 and Z2.0., in LVV against Vs30 and Z2.0.


Northern Death Valley Fault ZoneNorthern Death Valley Fault ZoneFurnace Creek M7.5 Scenario Ruptures, GM in Las Vegas Valley

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00

Site Vs30, km/s

0.3-Hz E3D PGV, meter/sec

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from SE

Rupture from SE

Rupture from SE

Rupture from SE

Rupture from SE

Vs30 affecting 1.5-km waves!


Northern Death Valley Fault ZoneNorthern Death Valley Fault ZoneFurnace Creek M7.5 Scenario Ruptures, GM in Las Vegas Valley

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Basin Depth Z2.0, km

0.3-Hz E3D PGV, meter/sec

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from NW

Rupture from SE

Rupture from SE

Rupture from SE

Rupture from SE

Rupture from SE


ConclusionsConclusions

Students can use MA-CME to set problems up, but Students can use MA-CME to set problems up, but plotting and visualizing are still lots of work.plotting and visualizing are still lots of work.

Scenario Results:Scenario Results: M5.0 Frenchman Mtn.– high PGV accompanied by M5.0 Frenchman Mtn.– high PGV accompanied by

short duration.short duration. M7.5 Genoa–Mt. Rose– Reno basin gets 5 times the M7.5 Genoa–Mt. Rose– Reno basin gets 5 times the

PGV of any other.PGV of any other. M7.5 No. Death Valley– rupture toward city produces M7.5 No. Death Valley– rupture toward city produces

up to 15 times the PGV as rupture away.up to 15 times the PGV as rupture away.• At long periods, 0.3 Hz, E3D is producing huge uncertainties At long periods, 0.3 Hz, E3D is producing huge uncertainties

in PGV.in PGV.

Documents

Seismic Shaking in Nevada’s Urban Areas: Computing Simple Scenarios