Assembling So. Nevada Geophysical Data to Model Seismic Response in Las Vegas Valley John N. Louie &...

Assembling So. Nevada Assembling So. Nevada Geophysical DataGeophysical Data

to Model Seismic Responseto Model Seismic Responsein Las Vegas Valleyin Las Vegas Valley

John N. Louie & John G. AndersonJohn N. Louie & John G. Anderson

Seismological Lab, UNRSeismological Lab, UNR

May 2002 - May 2005May 2002 - May 2005

J. Louie @ LLNL 10/22/2004J. Louie @ LLNL 10/22/2004

LVVSR Components @UNRLVVSR Components @UNR

Model AssemblerModel Assembler• Enables LLNL to use existing knowledgeEnables LLNL to use existing knowledge• Adding new data; interoperation and archivingAdding new data; interoperation and archiving

Shallow shear-velocity transectsShallow shear-velocity transects• Extensive reconnaissance dataExtensive reconnaissance data

E3D sensitivity studiesE3D sensitivity studies• Place facilities and expertise at UNRPlace facilities and expertise at UNR• Guide model assemblyGuide model assembly


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.input.

ModelModelAssemblerAssembler


Jachens, 1999 GB Classified GeologyJachens, 1999 GB Classified Geology


Regional Basin Regional Basin

DepthsDepthsJachens and Blakely, USGSJachens and Blakely, USGS

Sedimentary and VolcanicSedimentary and Volcanic

Derived from Basin GravityDerived from Basin Gravity


Model Assembler stitches together Langenheims’s thickness model for the Las Vegas basin, and basin depths estimated by a bedrock proximity rule from a

geologic map of the southwestern US. Map views of vertically averaged velocities in the Vp output of MA are made with the JRG tool.

Precedence RulePrecedence Rule


Minimum Basin Thickness Test

ModelAssembler interpolates basin depth data by distance-weighted averaging of all data points within a radius of the grid point. (Here the radius

was 1 km.) So bedrock areas within a radius of a basin point can receive small thicknesses. A minimum basin thickness rule controls the area of bedrock after interpolation. There is no effect on proximity basin-depth

estimates.

Interpolation RuleInterpolation Rule


Comparison of Regional Basin Estimators

Rogers’s March ‘02 5% topographic gradient result is above. Bedrock is blue and

basins are yellow. (Only showing surface velocity.)

Louie’s July ‘02 ModelAssembler 2.0 result is

below. Bedrock is red and basins are green-to-blue. (Showing 20-km vertical

velocity average.)

The bedrock nature of flat Pahute Mesa is now shown, but some Tertiary sediments like the Funeral Fm. in Death Valley also show as bedrock.

LV

LV

SM

SM

PMPM

PM

DVDV

DVDV


Model Assembler Operation OutlineModel Assembler Operation Outline

Documents the methods in MA

An outline in place of a complicated flowchart.

Guidance to users in this color.Guidance to users in this color.


1. Self-document and get infile name from command lineUsage: java ModelAssembler file.in > file.out

Run from UNIX command line.

The infile is a control file, in a format identical to that used by E3D, containing additional control lines ignored by E3D. MA reads its additional lines and several E3D control lines.

MA acts as a preprocessor for E3D by helping to set up the E3D MA acts as a preprocessor for E3D by helping to set up the E3D control file as well as the multi-Gb grid inputs for E3D.control file as well as the multi-Gb grid inputs for E3D.

2. Read infile to a Vector of Strings, one per line Vector input = ModelAssembler.readInput(infile);

The infile (control file) is simply read into a series of strings, one per line, including all comments and lines for E3D ignored by MA.



3. Parse input Vector to set up grid class with parameters Grid grid = new Grid(input);The infile strings are parsed to identify the unique “grid” control line, which

sets the geographic location, orientation, and sampling of the 3-d grid.

The translation between lat and lon and grid coordinates uses a flat-earth Cartesian projection accurate only at the midpoint of the grid. Grid axes follow rhumb lines and not great circles.

4. Parse input Vector to set up needed classes and parameters, and read data files, producing ordered precedence Vector of class Fill objects grid.preced = Fill.setupInput(grid, input); Parses basin and geotech lines from control file.

Based on order of basin and geotech lines in control file, arranges which Based on order of basin and geotech lines in control file, arranges which detailed data sets will substitute for (take precedence over) regional detailed data sets will substitute for (take precedence over) regional background data sets, where there is overlap.background data sets, where there is overlap.

Opens and reads the geological data from the files the control lines point to.

Geological data are always georeferenced, and supplied to MA as editable Geological data are always georeferenced, and supplied to MA as editable text files with points in any order.text files with points in any order.



5. Compute basin thickness at all surface points of grid grid.setupThicks(); Interpolates basin thickness at each surface point of grid from

precedence list of basin data sets.

Sorting out closest basin data points for each grid surface point from unordered data vectors is now computationally inefficient (done by brute force) and time consuming.

The interpolation of basin thickness is a distance-weighted average of The interpolation of basin thickness is a distance-weighted average of all basin thickness data points (not geographically superceded) falling all basin thickness data points (not geographically superceded) falling within a radius of the grid surface point.within a radius of the grid surface point.

A rule controls when small interpolated thicknesses are considered to be zero.

The search radius for data points is a parameter set for each data set in The search radius for data points is a parameter set for each data set in each basin line in the control file. The radius controls the 3d effect.each basin line in the control file. The radius controls the 3d effect.

Where no data points are within radius, the location is assumed to be Where no data points are within radius, the location is assumed to be bedrock, outside any basin.bedrock, outside any basin.



6. Compute geotechnical shear velocity at all surface points of gridgrid.setupGeotech(); Interpolates geotechnical shear velocity at each surface point of Interpolates geotechnical shear velocity at each surface point of

grid from precedence list of geotech data sets.grid from precedence list of geotech data sets.

The interpolation of geotechnical velocities is a distance-weighted The interpolation of geotechnical velocities is a distance-weighted average of all geotechnical data points (not geographically average of all geotechnical data points (not geographically superceded) falling within a radius of the grid surface point.superceded) falling within a radius of the grid surface point.

The search radius for data points is a parameter set for each data The search radius for data points is a parameter set for each data set in each geotech line in the control file.set in each geotech line in the control file.

Where no data points are within radius, the NEHRP B-C Where no data points are within radius, the NEHRP B-C Boundary 30-m shear velocity of 0.76 km/s is assumed outside Boundary 30-m shear velocity of 0.76 km/s is assumed outside basins, and the NEHRP C-D Boundary 30-m shear velocity of basins, and the NEHRP C-D Boundary 30-m shear velocity of 0.35 km/s is assumed inside basins.0.35 km/s is assumed inside basins.



7. If requested write Field (2000, 2001) amplifications for all surface points of grid grid.writeAmplif(input); Computed directly from interpolated basin thickness and geotechnical velocity.

8. Write binary grid files given precedence Vector grid.writeGrids();Interpolates grid depth-point properties from rules programmed for properties versus

depth inside and outside basins.

Rules control estimation of other properties from the property set by the rule for a particular geology and depth.

Within basins, a rule sets the density-versus-depth profile (Jachens and Blakely model Within basins, a rule sets the density-versus-depth profile (Jachens and Blakely model from oil-well logs in central Nevada); an equation estimates Vp (km/s) from density from oil-well logs in central Nevada); an equation estimates Vp (km/s) from density (g/cc)– (g/cc)– {qv = density/0.23; vp = qv*qv*qv*qv*0.3048/1000);}{qv = density/0.23; vp = qv*qv*qv*qv*0.3048/1000);}; ; and Vp/Vs is assumed to be the square root of three to estimate Vs.and Vp/Vs is assumed to be the square root of three to estimate Vs.

Outside and under basins, a rule sets the Vp-versus-depth profile- the profile used by Outside and under basins, a rule sets the Vp-versus-depth profile- the profile used by the SGBDSN for earthquake location; an equation (inverse of above) determines the SGBDSN for earthquake location; an equation (inverse of above) determines density from Vp; and then the same Vp/Vs ratio is applied.density from Vp; and then the same Vp/Vs ratio is applied.

Properties at depths between control-point depths in the rules are linearly interpolated.Properties at depths between control-point depths in the rules are linearly interpolated.(more…)



8 (continued). Write binary grid files given precedence VectorGeotechnical velocities are thickness-weighted and slowness-averaged Geotechnical velocities are thickness-weighted and slowness-averaged

into the shear velocities of the upper grid zones.into the shear velocities of the upper grid zones.

Where basin depths are less than the grid spacing dh, geotechnical, basin, Where basin depths are less than the grid spacing dh, geotechnical, basin, and bedrock velocities are all thickness-weighted and slowness-averaged and bedrock velocities are all thickness-weighted and slowness-averaged into the shear velocity of the upper grid zone.into the shear velocity of the upper grid zone.

Except in the uppermost zone, to depth dh, there is no averaging across Except in the uppermost zone, to depth dh, there is no averaging across basin boundaries. A grid zone is either all in the basin or it is all in the basin boundaries. A grid zone is either all in the basin or it is all in the bedrock.bedrock.

Given the pre-computed interpolated basin thicknesses and geotechnical velocities, following the profile and equation rules to compute the properties at the grid zone depths is rapid, and writing large grid volumes is not slow. All these operations could be done inside E3D.

9. Write (altered) input file to standard out ModelAssembler.outputInput(input);MA writes a new version of the control file for input to E3D, adding MA writes a new version of the control file for input to E3D, adding

translation of lat and lon given for source and sac lines to grid l, m, n translation of lat and lon given for source and sac lines to grid l, m, n coordinates.coordinates.



Illustrate Models with Field (2001) Amplification-MappingIllustrate Models with Field (2001) Amplification-Mapping

To visualize 1-10 km basin depths together with shallow To visualize 1-10 km basin depths together with shallow geotechnical velocities.geotechnical velocities.


How to InterpolateHow to InterpolateRandomly Spaced Measurements?Randomly Spaced Measurements?

ModelAssembler does the gridding of arbitrarily ModelAssembler does the gridding of arbitrarily located geological data.located geological data. Basin thicknesses and geotechnical velocities.Basin thicknesses and geotechnical velocities. Data are geo-referenced to points on a map.Data are geo-referenced to points on a map.

MA averages and interpolates among points on MA averages and interpolates among points on a map.a map. If grid zone contains one or more measurements, If grid zone contains one or more measurements,

average them.average them. If not, extrapolate from nearby measurements.If not, extrapolate from nearby measurements. Use default properties if no data “nearby.”Use default properties if no data “nearby.”


How to Interpolate Randomly Spaced Measurements?How to Interpolate Randomly Spaced Measurements?

Assign value of Assign value of nearest neighbornearest neighbor within search radius within search radius



Distance-weighted averageDistance-weighted average of all within search radius of all within search radius



Distance-weighted average of Distance-weighted average of closest in each quadrantclosest in each quadrant


Average Nearest in Each QuadrantAverage Nearest in Each Quadrant


Observations on InterpolationsObservations on Interpolations ““Nearness” radius setting has big effect.Nearness” radius setting has big effect.

Default properties differ sharply from local data.Default properties differ sharply from local data.

Nearest-neighbor looks “geological.”Nearest-neighbor looks “geological.” May represent spatial variability, but low confidence in May represent spatial variability, but low confidence in

extrapolated values.extrapolated values.

Average of all nearby data is too smooth.Average of all nearby data is too smooth. Misrepresents spatial variability, but gives high Misrepresents spatial variability, but gives high

confidence in regional average values.confidence in regional average values.

Used by MA3 for basin thickness and geotechnical data.Used by MA3 for basin thickness and geotechnical data.

Average of nearest data in 4 directions seems more Average of nearest data in 4 directions seems more

realistic. realistic. Still requires making a geologic model.Still requires making a geologic model. Retains some of the measured spatial variability.Retains some of the measured spatial variability.

Extrapolating averages gives higher confidence.Extrapolating averages gives higher confidence.


Most of Strip, Downtown; south side of Valley only

Las Vegas Transect MeasurementsLas Vegas Transect Measurements


V100 echoes V30

Las Vegas Transect MeasurementsLas Vegas Transect Measurements


Geologic Info to Predict VGeologic Info to Predict Vss

NSL, July ‘03, sponsored by LLNL

Can soil maps predict VCan soil maps predict Vss??


Does extrapolating VDoes extrapolating Vs s work? work? VVss assigned to soil-map units using central-City measurements. assigned to soil-map units using central-City measurements.

Later, outlying measurements (B. Luke, UNLV) not predicted by maps.Later, outlying measurements (B. Luke, UNLV) not predicted by maps.


Does extrapolating VDoes extrapolating Vs s work? work? VVss assigned to soil-map units using central-City measurements. assigned to soil-map units using central-City measurements.

Later, outlying measurements (B. Luke, UNLV) not predicted by maps.Later, outlying measurements (B. Luke, UNLV) not predicted by maps.

1 23

4


How to Extrapolate Shallow VHow to Extrapolate Shallow Vss Can we simply extrapolate measurements throughout basin?Can we simply extrapolate measurements throughout basin? No, need guidance of a geologic model.No, need guidance of a geologic model.


LVVSR Components @UNRLVVSR Components @UNR

Model Assembler 3.6.1 Delivery Model Assembler 3.6.1 Delivery to LLNLto LLNL

• Incorporates stratigraphic model Incorporates stratigraphic model for LVVfor LVV

• Adjusts regional assumptions to fit Adjusts regional assumptions to fit LVV dataLVV data


How to Extrapolate Shallow VHow to Extrapolate Shallow Vss Correlate 75 Vs measurements against stratigraphic model.Correlate 75 Vs measurements against stratigraphic model. Stratigraphy interpolated between >500 water-well logs.Stratigraphy interpolated between >500 water-well logs.


Extrapolated vs. MeasuredExtrapolated vs. Measured Comparisons along Cheyenne-to-Tropicana transect.Comparisons along Cheyenne-to-Tropicana transect.


How to Extrapolate Shallow VHow to Extrapolate Shallow Vss With subsurface information, prediction is better than with soil map.With subsurface information, prediction is better than with soil map.


How to Extrapolate Shallow VHow to Extrapolate Shallow Vss Well-log correlations predict measurements at more sites than with Well-log correlations predict measurements at more sites than with

soil-map correlations.soil-map correlations. Hazard is underestimated at fewer sites.Hazard is underestimated at fewer sites.


Create Top Zone for E3D GridCreate Top Zone for E3D Grid Always Always

average on average on slowness.slowness.

Velocities Velocities from top 100 from top 100 meters of meters of stratigraphic stratigraphic model.model.

Deeper Deeper zones zones interpolate interpolate refraction refraction results.results.

Revise Revise defaults to defaults to match.match.


Integrate LV Results with RegionIntegrate LV Results with Region


SummarySummary Shallow Shear-Velocity ModelingShallow Shear-Velocity Modeling

Difficult to predict amplification from maps.Difficult to predict amplification from maps. Stratigraphic model now predicts measurements, Stratigraphic model now predicts measurements,

extends throughout urban Valley.extends throughout urban Valley. Shallow basin has remarkably constant Vs.Shallow basin has remarkably constant Vs.

Model AssemblerModel Assembler Interpolates point measurements.Interpolates point measurements. Averages data & models into grid.Averages data & models into grid. Incorporates stratigraphic model for shallow LVV.Incorporates stratigraphic model for shallow LVV. Regional assumptions adjusted to match LVV data.Regional assumptions adjusted to match LVV data.


New DeploymentNew Deployment


MA Java-C Conversion NotesMA Java-C Conversion Notes

A complete re-design of the C code, with A complete re-design of the C code, with help from Dr. Harris and Jeff Stuarthelp from Dr. Harris and Jeff Stuart

Uses void pointer and type-casting to Uses void pointer and type-casting to implement a single Vector structure that is implement a single Vector structure that is re-usable for different data typesre-usable for different data types fewer files and pointers need to be handledfewer files and pointers need to be handled


Java-C ConversionJava-C Conversion

For the Vector structure:For the Vector structure:

Explicit functions to allocate and release Explicit functions to allocate and release memory (for an instance of the structure) were memory (for an instance of the structure) were implementedimplemented• easier to check for memory leakseasier to check for memory leaks• clearer and more coherent codeclearer and more coherent code



Additional structures also have new() and Additional structures also have new() and delete() functions that specifically allocate and delete() functions that specifically allocate and release memoryrelease memory easier to detect memory leakseasier to detect memory leaks

Static memory allocation is used as much as Static memory allocation is used as much as possible for the implementation of the various possible for the implementation of the various structuresstructures to ease the task of handling memory allocation and to ease the task of handling memory allocation and

releaserelease



The new implementation is still a The new implementation is still a direct translation of the original java direct translation of the original java code.code.

For example, each “.java” file is For example, each “.java” file is converted into a “.h” and a “.c” file.converted into a “.h” and a “.c” file.


Speed ComparisonSpeed Comparison

Testing with an Intel Pentium 4 machine Testing with an Intel Pentium 4 machine with sample parameters:with sample parameters: The C code execution finishes in about 3.5 The C code execution finishes in about 3.5

minutes, compared to 4.5 minutes for the minutes, compared to 4.5 minutes for the original Java codeoriginal Java code• ~20% performance increase~20% performance increase• Much additional optimization still to doMuch additional optimization still to do


Result ComparisonResult Comparison Testing on Mac OS10.3, the C conversion Testing on Mac OS10.3, the C conversion

generates effectively identical binary generates effectively identical binary output files (i.e., den.flt, vs.flt, vp.flt,) output files (i.e., den.flt, vs.flt, vp.flt,) compared to the java codecompared to the java code

- =


Required MA4 EnhancementsRequired MA4 Enhancements Include regional geophysical grids in MA.Include regional geophysical grids in MA.

The “grids” will be supplied as property-vs-depth The “grids” will be supplied as property-vs-depth profiles.profiles.

Alterations to the geotech operations to average Alterations to the geotech operations to average in full profiles instead of the Vin full profiles instead of the V3030 values put in now. values put in now. Geotech and regional profiles in Luke’s format.Geotech and regional profiles in Luke’s format.

All averaging and interpolation of Vp and Vs done All averaging and interpolation of Vp and Vs done arithmetically on slowness (inverse velocity, for arithmetically on slowness (inverse velocity, for conservation of travel time). Densities combine conservation of travel time). Densities combine arithmetically for conservation of mass.arithmetically for conservation of mass. Approximate completion date: mid-MayApproximate completion date: mid-May


Other MA4 EnhancementsOther MA4 Enhancements

Optional control from basin, profile, and geotech Optional control from basin, profile, and geotech parameter lines on the type of interpolation parameter lines on the type of interpolation used: nearest neighbor, linear, distance-used: nearest neighbor, linear, distance-weighted, etc.weighted, etc. expected completion date: before mid Aprilexpected completion date: before mid April

Precision control by truncation of results to 3 or Precision control by truncation of results to 3 or 4 significant figures, to assure identical output 4 significant figures, to assure identical output across platforms and compilersacross platforms and compilers expected completion date: before Aprilexpected completion date: before April


ReMi measures Rayleigh dispersion with linear refraction arrays.ReMi measures Rayleigh dispersion with linear refraction arrays.

Shallow Shear-Velocity TransectsShallow Shear-Velocity Transects


ReMi has classified hard and soft sites around the world by measuring V30, average shear velocity to 30 m depth.

Refraction Microtremor for Shallow Shear VelocityRefraction Microtremor for Shallow Shear Velocity


Transect DataTransect Data

High-velocity picks at >0.4 sec period are unreliable.

Picks at 0.1-0.3 sec illustrate velocity differences to 100 m depth.

Assembling So. Nevada Geophysical Data to Model Seismic Response in Las Vegas Valley John N. Louie &...

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