Southern California Earthquake Center SCEC Unified California Velocity Model

1. Southern California Earthquake CenterSCEC Unified CaliforniaVelocity Model Patrick Small Research Programmer

2. UCVM Features • Provides a uniform query interface to several California velocity models. Models may be queried by (lon,lat,depth) or (lon,lat,elev). • Contains both a Linux command line query tool and C programming interface • Easily combine two or more regional velocity models together into one meta-model. Models are tiled in specified order. • Provides access to several additional statewide datasets: • digital elevation model • Vs30 map • GTL based on Ely’s method

3. Supported Models • UCVM supports these regional models: • SCEC CVM-H 11.2.0 • SCEC CVM-S and SCEC CVM-SI (Po Chen’s iterates) • USGS Central California (cencalvm) • Lin-Thurber California Statewide • Rob Graves Cape Mendocino • Hadley-Kanamori 1D • Any CMU/SCEC formatted Etree • UCVM supports these geo-technical layer models: • Ely Vs30-derived GTL

4. Coverage • UCVM region encompasses California and portions of surrounding States to support future 1Hz CyberShake simulations. • Coverage region is a rotated 1800 km x 900 km x 112.5 km box with origin at (-129.75 DD, 40.75 DD)

5. Inputs and Data Sets • DEM: USGS NED 1 arc sec topo with ETOPO1 for bathymetric • Vs30: Wills 2006 California high-rez and Wald 2007 global • Regional Models: C/Fortran codes, with model data stored in Etrees, binary flat files, Voxets, or simple tables. • Projections: Any projection supported by the Proj.4 projection package

6. Architecture

7. Query Tool • The command line tool, ucvm_query, is provided to query models: • usage: ucvm_query [-m models<:ifunc>] [-c coordtype] [-f config] <-z zmin,zmax> < file.in • Flags: • -h This help message. • -m Comma delimited list of crustal/GTL models to query in order of preference. GTL models may • optionally be suffixed with ':ifunc‘ to specify interpolation function • -c Coordinate mode: geo-depth (gd, default), geo-elev (ge). • -f Configuration file. Default is ./ucvm.conf. • -z Optional depth range for gtl/crust interpolation • Input format of file.in is: • long lat z • Output format is: • X Y Z surf vs30 cr_modelcr_vpcr_vscr_rhogtl_modelgtl_vpgtl_vsgtl_rhocmb_algocmb_vpcmb_vscmb_rho

8. Query Example Query example with CVM-S: [patrices@aftershockbin]$ ./ucvm_query -m cvms -f ../conf/aftershock/ucvm.conf Using Geo Depth coordinates as default mode. -118.0 34.0 0.0 -118.0 34.0 100.0 -118.0 34.0 1000.0 <Cntrl-D> -118.0000 34.0000 0.000 295.679 390.000 cvms 696.491 213.000 1974.976 none 0.000 0.000 0.000 crust 696.491 213.000 1974.976 -118.0000 34.0000 100.000 295.679 390.000 cvms 1683.174 603.470 2130.773 none 0.000 0.000 0.000 crust 1683.174 603.470 2130.773 -118.0000 34.0000 1000.000 295.679 390.000 cvms 3660.809 2056.628 2443.042 none 0.000 0.000 0.000 crust 3660.809 2056.628 2443.042 [patrices@aftershock bin]$

9. Query Inputs and Outputs • Inputs: • One or more points of (longitude, latitude, Z) • Outputs (for each point): • Surface elevation at that (long, lat) • Vs30 at that (long, lat) • Crustal Vp, Vs, density • GTL Vp, Vs, density (if a GTL enabled) • Combined Crustal/GTL Vp, Vs, density

10. Velocity Model Requirements • To be integrated into UCVM, velocity models must provide the following: • C/Fortran codes and libraries that can be linked *statically* • Query by (lon, lat ,z) where z is some vertical measure that can be translated to depth/elevation. • Vp, Vs, and density (any units). • Ideally have a memory footprint <1 GB to facilitate large-scale parallelization. • Version identifier • Functions: Initializer, Get Version, Query Point, and (ideally) Finalizer • The velocity model may internally use any projection and data storage format

11. Definitions and Conventions • Depth: Measured in meters relative to ground/water, ground/air interface, positive down. Constrained to >= 0.0. UCVM translates model depth references if different from this definition. • Elevation: Measured in meters relative to MSL, positive up. UCVM translates model elevation references if different from this definition. • Geographic coordinates: Longitude and latitude are measured in DD, longitude west is negative. • Vp and Vs: Measured in m/s. • Density: Measured in kg/m^3. • “No data” values: Value is set to 0.0.

12. Parallelization • Tested with 3300+ cores querying CVM-H to produce 435 B point M8 mesh on NICS Kraken (1.5 Hrs) • Memory overhead per core may be significant depending on selection of models: • Eg: CVM-H 11.2 (1.3 GB), CVM-SI (1.8 GB), CVM-S (300 MB) • Recommend delivering statewide model as an Etree which can be cached more effectively, reducing memory requirements • Etrees on Lustre file systems require special handling: • Setup of Cray iobuf module • Apply patch to the Euclid Etree source.

13. Additional Capabilities • User may easily extend UCVM with new models using the C API. • 3D interfaces between overlapping models may be numerically smoothed to remove sharp discontinuities with an inverse distance weighting function. • A model or combination of models may be exported as a SCEC-formatted Etree with variable resolution, using the mininum Vs and max frequency relation: local resolution = local Vs / (fmax * ppwl) • Generic ArcGIS extraction tool and API for combining multiple geo-referenced GridFloat data sets and querying them by (lon, lat). Useful for DEMs and Vs30 maps but can be applied to any GIS dataset.

14. UCVM DEM Sourced from USGS NED 1 arcsec and ETOPO1 datasets

15. UCVM Vs30 Sourced from Wills 2006 and Wald 2007 Vs30 data

16. UCVM GTL Ely Vs30-derived GTL, using Wills/Wald Vs30 map

17. Extensibility Beyond California • UCVM may be configured for regions outside of California • The required data inputs for an arbitrary region are: • Definition of coverage region and projection (any supported Proj.4 proj) • Digital elevation data in ArcGISgridfloat format • Vs30 data in ArcGISgridfloat format • A velocity model implemented as C/Fortran code.

18. UCVM Utah • An example installation of UCVM for northern Utah (with Magistrale’s Wasatch Front model):

19. Technical Notes • DEM/Vs30 data is stored internally as a 2D Etree • In many cases you may not query two versions of the same model simultaneously (eg: CVM-H 5.3 and CVM-H 11.2) due to symbol name clashes. Workarounds and exceptions: • If only the model data has changed (i/f is the same), simply update model path in ucvm.conf • If i/f has changed between versions, setup a UCVM installation for each model version, and point to the appropriate install depending on which model you wish to query • Etrees and patches: UCVM can use up to 100 SCEC Etrees or model patches simultaneously. • Combining overlapping models: UCVM simply queries models in the order they are given. With the “patch” utility, new patch models with numerical smoothing of 3D regions can be included to blend overlaps, but this is fairly crude.

20. Resources • UCVM Overview: • http://scec.usc.edu/scecpedia/UCVM • UCVM API Documentation: • http://scec.usc.edu/scecpedia/UCVM_API • Software Download • UCVM SVN: https://source.usc.edu/svn/ucvm • Requires Euclid Etree Library, Proj.4 Library, Model Libraries

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