The SCEC Unified Community Velocity Model (UCVM) software is used to access information, including estimated Vp and Vs seismic wave velocities and density, about the earth's crust.

UCVM provides seismic velocity information for several California regions. Seismic velocities of rocks and sediments at shallow depths determine how strongly an area will shake. By assigning velocities to rock types in the 3-D geologic model, geologists can gain an understanding of the extent of areas of low shear velocity that are most likely to experience localized strong shaking and future earthquake damage. An important application for the models accessible through UCVM is for use in computer simulations of California earthquakes.

The Unified Community Velocity Model C-language (UCVMC) software framework is a collection of software tools designed to provide a standard interface to multiple, alternative, California velocity models. UCVMC development is an interdisciplinary research collaboration involving geoscientists, computer scientists, and software developers. UCVMC is used in high resolution 3D wave propagation simulations for California.

The map below shows the coverage regions for currently supported California velocity models that are accessible through UCVMC. Each of the models shown is considered a regional velocity model. Typically the models return values down to about 50km or 100km, but most models are undefined below 100km. For earth material properties below 100km, global seismic velocity models, such as the Preliminary Earth Reference Model (PREM), are possible alternative models.

Map shows coverage region for California CVMs registered into UCVMC. Coverage region for UCVM 2D maps (yellow) overlayed upon regions of various California 3D velocity models (CVM-S4: red, CVM-S4 geotechnical regions: red polygons, CVM-H high resolution: small light blue square, CVM-H low resolution: larger light blue square, USGS High Resolution Bay Area: small white rectangle, USGS Low Resolution Bay Area: large white rectangle, CVM-S4.26, CVM-S4.26M01: green, CCA 06: small yellow, CS17.3, CS17.3-H: large orange rectangle, Havard San Joaquin Basin Model: small orange rectangle, Havard Santa Maria Basin Model: orange square, CS18.5 Cypershake Study's Tiled Velocity Model: blue) : Coverage.kml

UCVMC software repository contains a software codebase developed by Philip Maechling, Mei-Hui Su, David Gill, Patrick Small, and others at SCEC. UCVMC is released as open-source scientific software under an Apache 2 software license.

UCVM was developed with support from National Science Foundation (NSF), US Geological Survey (USGS), and other sources.

Testing UCVMC on all possible combinations of operating sysetms and software stacks requires more software developer resources than currently available. So, we have defined a UCVMC reference software stack that we use to develop and test the software. This UCVMC distrbution has been shown to work on the following reference software stack. It may work on other software stacks, also, but this is the supported software environment.

• Linux operating system (e.g. CentOS 7 Linux) x86_64-linux
• GNU gcc/gfortran compilers version 4.8.5
• Python 2.7.11 (Anaconda 4.0.0 (64-bit))
• Autotools build software for Linux
• Automake, Autoconf build tools for Linux
• Git client

External Libraries installed by UCVMC

• Euclid Etree library: http://www.cs.cmu.edu/~euclid/ (provided during installation)
• Proj.5 projection library: http://trac.osgeo.org/proj/ (provided during installation)

Optional Software for building MPI binaries:

• openmpi 1.8.8

Once the target computer has the required software tools installed, the basic install of UCVMC is:

• git clone https://github.com/SCECcode/UCVMC.git
• cd UCVMC/largefiles
• ./get_large_files.py
• ./check_largefiles_md5.py
• ./stage_large_files.py
• cd ..
• ./ucvm_setup.py

The get_large_files.py and ucvm_setup.py scripts run in a terminal window and print text questions to the user. The user types answers to the questions in the terminal window. The retrieval script asks the user which velocity model they would like to stage into the local system and the install script asks the user which velocity models they would like to install from retrieved model list: ( CVM-H v15.1, CVM-S4, CVM-S4.26, CVM-S4.26.M01, CCA06, CS17.3, CS17.3-H, and USGS CenCal). Several models are very large. CCA06, CS17.3 and CS17.3-H are 9.2G, 72G and 72G respectively. We recommend that the user only retrieve needed models and install all retrieved models.

The script will then automatically compile, build, and install the selected models.

If a GNU-based MPI compiler is detected, the MPI version of several utilities are created, including ucvm2mesh_mpi, ucvm2mesh_mpi_layer, ucvm2etree_mpi, and basin_query_mpi are built. Otherwise, only the serial versions for these programs are built.

The main UCVMC configuration file is ${UCVM_INSTALL_DIR}/conf/ucvm.conf. This file defines the paths to all configured models and maps, and it defines selected model flags, such as CVM-H USE_GTL. The UCVM installer sets up this ucvm.conf file automatically.

In most cases, the user does not need to edit the UCVMC/conf/ucvm.conf. However, in some circumstances, such as if the user wants to move the UCVMC installation directory, or configure the behavior of the CVM-H model, the user might want to edit the ucvm.conf file. Please see the User Guide for more details on how to edit the UCVMC/conf/ucvm.conf configuration file.

The following California velocity models packages are included as part of a standard UCVMC installation. Each model is assigned an abbreviation, and these abbreviations are used to specify the models when making UCVM queries. The model abbreviations used by UCVM are defined in following tables:

A state-wide California standard topography map is distribued with UCVMC. This is a statewide topography map, that also includes statewide Vs30 values, combined into an etree structure.

Online UCVMC documentation is available at:

• https://github.com/SCECcode/UCVMC/wiki

Additional documentation advanced features and previous versions of UCVM are posted at:

• http://scec.usc.edu/scecpedia/UCVMC

More Installation instruction:

• Additional guidelines for building UCVMC

Issue Tracking:

• GitHub: https://github.com/SCECcode/UCVMC/issues

Email:

• Contact: software@scec.usc.edu

If you use the UCVM software in your research, please include a reference to the following publication in your research publications. References help us obtain continued financial support for the development of the software. The preferred reference for the UCVM software is:

Small, P., Gill, D., Maechling, P. J., Taborda, R., Callaghan, S., Jordan, T. H., Ely, G. P., Olsen, K. B., & Goulet, C. A. (2017). The SCEC Unified Community Velocity Model Software Framework. Seismological Research Letters, 88(5). doi:10.1785/0220170082.

UCVMC is released under the Apache 2.0 license. Please see the LICENSE file for distribution license and disclaimers.