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The SCEC Community Velocity Model - Harvard (CVM-H) is a velocity model of crust and upper mantle structure in southern California developed by the SCEC community for use in fault systems analysis, strong ground motion prediction, and earthquake hazards assessment. The model describes seismic P- and S-wave velocities and densities, and is comprised of basin structures embedded in tomographic and teleseismic crust and upper mantle models.

This latest release of the CVM-H (11.2.0) represents the integration of various model components, including fully 3D waveform tomographic results. The CVM-H 11.2.0 consists of basin structures defined using high-quality industry seismic reflection profiles and tens of thousands of direct velocity measurements from boreholes (Plesch et al., 2009; Süss and Shaw, 2003). The basin structures are also compatible with the locations and displacements of major faults represented in the SCEC Community Fault Model (CFM) (Plesch et al., 2007). These basin structures were used to develop travel time tomographic models of the crust (after Hauksson, 2000) extending to a depth of 35 km, and upper mantle teleseismic and surface wave models extending to a depth of 300 km (Prindle and Tanimoto, 2006). These various model components were integrated and used to perform a series of 3D adjoint tomographic inversions that highlight areas of the model that were responsible for mismatches between observed and synthetic waveforms (Tape et al, 2009). Sixteen tomographic iterations, requiring 6800 wavefield simulations, yielded perturbations to the starting model that have been incorporated in the latest model release. CVM-H 11.2.0 also incorporates a new Moho surface (Yan and Clayton, 2007) and an upgraded geotechnical layer (GTL) based on a Vs30 map (Ely 2010), the Vp-density scaling relationship, and the code that delivers the model. 

== Current Release ==

SCEC CVM-H version 11.2.0 is scheduled to be released on Friday 25 February 2011.

[[File:CVM-H11.2.png|256px|thumb|right|The latest version of the SCEC Community Velocity Model (CVM-H 11.2) includes basin structures embedded in the 3D waveform inversion model of Tape et al. (2009), and an explicit representation of the Moho (after Yan and Clayton, 2007; Chulick and Mooney, 2002).]]

== Features of Current CVM-H ==
The newest version of CVM-H provides three primary new capabilities:
*Vs30-based arbitrary precision GTL
*Extended Region using 1D background model
*Standardized interface for removing topography

== Software Dependencies ==
The following software is required to build and run CVM-H.
 
*UNIX operating system (Linux, Solaris, MacOS) 
*GNU make 
*tar for opening the compressed files 
*Optionally GTS (GNU Triangulated Surface Library) for cvmdist http://gts.sourceforge.net 
*Optionally GMT (Generic Mapping Tools) to generate plots from vx_slice http://www.soest.hawaii.edu/gmt/

== Installation and Use of CVM-H ==
To install and use the CVM-H, you need to download and build the CVM-H software distribution. There are detailed installation instructions on the [[CVM-H User Guide]]. The main steps involved in installing CVM-H include:
#The software can be installed in an account on a Linux computer with at least 100G of disk storage and C compilers.
#From this Linux computer, start a web browser and point to this download page. Alternatively, you can download the files to a different machine and use FTP or SFTP to copy them over.
#Download the following two files (source, source md5sum) into a directory and run the md5sum program to confirm you have an undamaged version of the distribution files.
#Uncompress the distribution (tgz) files into a local directory on your computer.
#Build the executables by running the top level makefile.
#Confirm the code is built correctly by running UnitTests.
#Confirm the code runs correctly on your system by running AcceptanceTests.
#Use CVM-H for research purposes. 

== Download Latest Version: ==
*SCEC CVM-H: [http://hypocenter.usc.edu/research/cvmh/11.2.0/cvmh_11.2.0.tgz cvmh_11.2.0.tgz]
*md5sum: [http://hypocenter.usc.edu/research/cvmh/11.2.0/cvmh_11.2.0.tgz.md5 cvmh_11.2.0.tgz.md5]

== [[CVM Evaluation]] ==
We have introduced [[CVM Evaluation]] tests as part of the CVM-H release process. In our [[CVM Evaluation]] system, we use the latest version of CVM-H to build a velocity mesh for use in a 1Hz wave propagation simulation. We then run a wave propagation simulation using the each CVM mesh under evaluation, and we run goodness-of-fit measures that compare the simulation result against observation data (seismograms). The SCEC [[CVM Evaluation]] system is designed to compare simulation results for alternative CVM models.

== Alternative SCEC CVM's ==
As a part of the CVM-H release procedure, we are posting the "best available" versions of earlier, or alternative, SCEC CVM's. These software distributions represent the version of the CVM's used in our CVM evaluation tests. Our CVM evaluation system was used to evaluate the current version of CVM-H (v11.2). We also evaluated the following two alternative, or earlier, SCEC CVM's.
*[[CVM-S]] (CVM-4 with Geoff Ely bug fixes): [http://hypocenter.usc.edu/research/cvmtest/11.1.0_RC/cvm4_gely_20101209.tar cvm4_gely_20101209.tar]
*[[CVM-H v6.3capi]] (CVM-H v63 model w/ vx_lite and C API, w/o any GTL): [http://hypocenter.usc.edu/research/cvmtest/11.1.0_RC/cvmh_v63.tgz cvmh_v63.tgz]

== CVM-H Documentation ==
[[CVM-H User Guide]] includes installation instructions: 

== CVM-H Information Materials ==
These posters and presentations may contain information about earlier versions of CVM-H. However this overview information may still be useful to some users.
*[http://hypocenter.usc.edu/research/UCVM/CVM_H_11.2_summary.ppt Overview of CVM-H 11.2 (1Mb powerpoint file) ]
*[http://hypocenter.usc.edu/research/UCVM/Plesch_CVMH_PetaSHA_08.ppt Andreas Plesch Overview of CVM-H (2008) (7.4Mb powerpoint file)]
*[http://hypocenter.usc.edu/research/UCVM/CVM_H_scec2008poster.pdf CVM-H Poster SCEC Annual Meeting (2008) (1.8Mb pdf file) ]
*[http://hypocenter.usc.edu/research/UCVM/USR_Descriptions.pptx Overview of SCEC Unified Structure Representation (USR) Developments (4.2Mb powerpoint file) ]

== Development version ==

If you're interested in working with the latest development version of the platform, you can check it out from:
 svn co https://source.usc.edu/svn/cvmh/trunk

Details about working with the development version are provided in the User Guide.

== Technical Support ==

For assistance with the SCEC CVM-H, you may:
* Browse and submit new tickets at [http://northridge.usc.edu/trac/cvmh/ CVM-H Trac]
* Email software (at) scec.org with specific questions

== Software License ==

The CVM-H software is released under the Apache 2.0 license as described here [[CVM-H License]].

== Release History ==
*11.2 - February 2011 - This is the first release of CVM-H that includes the Vs30-based geotechnical layer and the vx_lite user interface. This version also introduces a date-based version numbering scheme (Year.Month.Revision).
*6.3capi - November 2010 - This is an interim version of CVM-H for use in testing and evaluation. This version includes an initial version of the vx_lite interface but does not provide the Vs30-based geotechnical layer. This version is distributed for completeness and we do not recommended its use by researchers.
*6.3 - August 2010 - This version CVM-H, released by the Harvard Structural Geology Group, removes all [[CVM-S]] geotechnical information and restores the original CVM-H material properties to all regions of the model.
*6.2 - August 2009 - This version of CVM-H includes modifications to top 300m material properties based on geotechnical information extracted from [[CVM-S]] as an interim approach to providing near surface geotechnical information into CVM-H material properties database.
*6.1 - January 2009 - This version of CVM-H incorporates tomographic inversion results from Carl Tape et al.
*5.3 - August 2008 - This is a version of CVM-H prior to integration of tomographic inversion results.

== Related Entries ==
*[http://structure.harvard.edu/ Harvard Structural Geology and Earth Resources Group Home Page]
*[http://structure.harvard.edu/cvm-h/ Harvard CVM-H Web Page]
*[[Goodness of Fit]]
*[[CVM-S]]
*[[CVM-H v6.3capi]]
*[[CVM Toolkit]]
*[[CVM Evaluation]]
*[[Community Velocity Model]]
*[[UCVM]]

== See Also ==
*[http://scec.usc.edu/scecpedia/software SCEC Software Downloads]
*[http://scec.usc.edu/scecpedia SCEC Wiki Main]
*[http://www.scec.org SCEC Home Page]

== References ==
#'''Suess, M. P., and J. H. Shaw, 2003:''' P-wave seismic velocity structure derived from sonic logs and industry reflection data in the Los Angeles basin, California, Journal of Geophysical Research, 108/B3.
#'''Plesch, A., C. Tape, J. H. Shaw, and members of the USR working group, 2009, CVM-H 6.0:''' Inversion integration, the San Joaquin Valley and other advances in the community velocity model, in 2009 Southern California Earthquake Center Annual Meeting, Proceedings and Abstracts, vol. 19, pp. 260–261. 
#'''Tape, C., Q. Liu, A. Maggi, and J. Tromp, 2009:''' Adjoint tomography of the southern California crust, Science, v. 325, p. 988-992.
#''' Ely, G., 2010:''' [http://earth.usc.edu/~gely/cvmh/ Vs30 Derived GTL]