CVM-H User Guide

User manual for the Southern California Earthquake Center

Community Velocity Model: SCEC CVM-H 11.1.0

Andreas Plesch, Carl Tape, John H. Shaw, Patrick Small, Geoff Ely

Harvard University, University of Southern California

January 21, 2011

This PDF file can be downloaded directly from: http://structure.harvard.edu/cvm-h/download/cvmh_manual.pdf

Overview

The SCEC CVM-H 6.2 is a 3D model of the elastic structure of southern California. It contains volumetric representations of compressional wave velocity (VP), shear wave velocity (VS), and density (�). It also contains three primary surfaces: the topological/bathymetric surface, the basement surface, and the Moho surface. The model is constructed from numerous datasets (S¨uss and Shaw, 2003) and has been used within parallel-computing based wavefield simulations of earthquakes within southern California (e.g., Komatitsch et al., 2004). See Section 6 for details.

Downloading CVM-H

1. Start at SCEC website: http://scec.usc.edu/scecpedia/CVM-H

2. Read the description of the model.

3. Navigate to the “Source Code” section and click the download link to download the latest version. NOTE: this file is large (500 MB), so the download make take awhile.

Requirements

CVM-H has no external software dependencies. The makefile is tailored for use with a GNU C compiler but it should compile with any modern C compiler.

Installation

• Download the latest version tarball and untar into a ./cvmh subdirectory with this command:

% tar zxvf cvmh_11.1.0_RC.tgz

• The package is built by executing the following commands:

% cd ./cvmh
% make clean;make all

• Ensure that the s/w is correctly built by running the unit tests. All tests should pass.

% cd ./test
% ./unittest

Utilities

The following executable utilities are provided:

vx

Original interface to Harvard's model. Accepts lon/lat/elev points from stdin and prints material properties to stdout. The original user guide can be found here .

vx_lite

Updated interface to Harvard's model that supports optional 1D background, Vs30 derived GTL, and querying by depth. Accepts lon/lat/z points from stdin and prints material properties to stdout.

vx_slice

Visualization utility for extracting a 2D horizontal slice of Vp, Vs, or Rho (density) from the model, suitable for plotting with a graphics package.

Querying for SoCal Material Properties on the Command Line

Two utilities are provided for querying the community velocity model, vx and vx_lite. The vx utility is the original interfance to Harvard's model. It is described in the PDF linked in the previous section. The vx_lite utility is a new SCEC-developed interface which supports a number of enhancements, including query by depth, extension of the coverage region with a SCEC 1D model, and replacement of the original GTL with a Vs30-derived GTL.

The command line format for vx_lite is as follows:

% vx_lite [-s] [-d] [-v] [< input_coords]

where the options:

-s

Instructs use of SCEC 1D background model

-d

Interpret z coordinate as depth from free surface

-v

Interpret z coordinate as elevation

input_coords

3D point specified as either (lon, lat, z (meters)) or (easting, northing, z (meters)), space delimited. Input coordinates can be specified interactively or redirected to stdin from a file.

Note: Options -d and -v are mutually exclusive. Specifying neither option instructs vx_lite to interpret the z coordinate as elevation offset from free surface.

The query data is printed to stdout, and this may be redirected to a file.

CVM-H defines a set of sample test points (given in ./bin/test_data/test.dat):

-125 35 -7777
-118.56 32.55 -2450
360061 3750229 -1400
-118.52 34.12 -1400
-116.40 32.34 -1000
376592 3773379 -1770
376592 3773379 -17700
408669 3766189 -3000

These may be submitted to vx_lite with this command:

% ./vx_lite -s -v < ./test_data/test.dat

The material properties at the sample points will be printed to stdout. You can expect to see the following output, annotated here with column headers. The three important fields are the last three, containing vp, vs, and rho.

     X               Y             Z       utmX        utmY      elevX       elevY      topo      mtop      base      moho  hr/lr/cm cellX     cellY     cellZ       tag        vp        vs       rho
  -125.000000       35.000000  -7777.00 -230844.88  3902223.73  -99999.00   -99999.00      0.00      0.00 -99999.00 -99999.00 bk  -99999.00   -99999.00 -99999.00     14.00   6300.00   3637.31   2859.77
  -118.560000       32.550000  -2450.00  353525.18  3602285.14  353625.00  3602375.00  -1114.91  -1150.00  -1327.54 -21571.67 lr  354000.00  3602000.00  -2400.00      2.00   5575.15   3132.10   2631.81
360061.000000  3750229.000000  -1400.00  360061.00  3750229.00  360125.00  3750125.00    -56.93    -50.00  -1404.07 -24868.83 lr  360000.00  3750000.00  -1400.00      2.00   4554.52   2313.56   2469.78
  -118.520000       34.120000  -1400.00  359819.67  3776309.78  359875.00  3776375.00    491.46    450.00     38.42 -28061.40 lr  360000.00  3776000.00  -1400.00      2.00   5066.61   2916.30   2545.10
  -116.400000       32.340000  -1000.00  556464.74  3578092.46  556375.00  3578125.00    780.43    750.00    616.39 -31413.62 lr  556000.00  3578000.00  -1000.00      2.00   5372.79   3024.30   2595.55
376592.000000  3773379.000000  -1770.00  376592.00  3773379.00  376625.00  3773375.00     99.38    100.00  -2374.53 -28165.35 hr  376552.25  3773500.00  -1800.00      3.00   4181.37   2432.22   2418.45
376592.000000  3773379.000000 -17700.00  376592.00  3773379.00  376625.00  3773375.00     99.38    100.00  -2374.53 -28165.35 cm  380000.00  3770000.00 -18000.00      2.00   6533.31   3776.40   2841.47
408669.000000  3766189.000000  -3000.00  408669.00  3766189.00  408625.00  3766125.00     93.89     50.00  -2820.45 -29799.86 hr  408552.25  3766250.00  -3000.00      2.00   4997.06   2889.03   2534.30

Querying for SoCal Material Properties in a C Program

SCEC has developed a C API to the Harvard model. The header containing the datatype and function definitions is located in ./src/vx_sub.h. By including this header in your source, and the libvxapi.a library at link time, your program can directly query CVM-H. See the cvm2mesh mesh extraction tool below for an example implementation that uses this API.

Known Issues

None.