VUME Upper Mantle of the Earth

Three-Dimensional Community Velocity Models

The 3D Community Velocity Model (CVM) provides a unified reference model for the several areas of research that depend of the subsurface velocity structure in their analysis. The velocity models are a Fortran code and associated files that are downloaded, compiled, and run locally. The user queries the models by creating an input file of latitude, longitude, and depth values, and the model returns Vp, Vs, and density at each of those points. Some web based interfaces to handle model queries have been developed and are available from the SCEC Community Modeling Environment.
The CVM is periodically updated as more data become available and as additional analyses of existing data allow improvement to model elements. Important in refining the CVM are geophysical and borehole data that enhance our understanding of basin structure and velocities of various soil and rock types.

SCEC Community Model.

Community Velocity Models, within SCEC, are computer programs and data files that provide information about earths material properties from the surface to depths below 100km. SCEC's community velocity models provide detailed 3D properties for southern California. Other seismological velocity models are avaiable for other regions. Other CVM's will have capabilities similar to SCEC CVM's.

The Southern California Earthquake Center (SCEC).

The Southern California Earthquake Center (SCEC) is a community of over 600 scientists, students, and others at over 60 institutions worldwide, headquartered at the University of Southern California. SCEC is funded by the National Science Foundation and the U.S. Geological Survey to develop a comprehensive understanding of earthquakes in Southern California and elsewhere, and to communicate useful knowledge for reducing earthquake risk.

The Wasatch Front CVM.

A three-dimensional Community Velocity Model was developed to provide a framework for simulating ground motion expected during an earthquake on the highly urbanized part of the Wasatch fault zone. The CVM provides researchers a unified subsurface velocity model to simulate effects including strong motion, seismicity location, and tomographic velocity. Elements that populate the CVM include: soil classes, basin geometry, basin-sediment interfaces, crustal tomography, and the Moho. The Wasatch Front CVM is based on earlier models developed by the Southern California Earthquake Center (SCEC). Presently, the CVM includes Cache, Weber/Davis, Salt Lake, and Utah basins. Future versions will expand the CVM to Tooele and Rush Valleys, Great Salt Lake Basin west of Antelope Island, and Wasatch Range back valleys.
The downloadable CVM version 3c includes Fortran 77 code with associated files that must be compiled (using a Fortran compiler on the users specific computer platform) and run locally. The CVM has been successfully compiled in Windows, using the g95 complier and MinGW. Input files must include latitude, longitude, and depth. The model returns Vp, Vs, and density for each input location.
While the Utah Geological Survey (UGS) provides the CVM to the public, the UGS does not provide support related to the CVM.

New Madrid region CVM.

The USGS has begun the development and construction of a community seismic velocity model to support general research in the New Madrid region as well as numerical simulations of earthquake rupture and seismic wave propagation due to a repeat of the 1811-1812 earthquakes. CVM has collected existing research regarding the P- and S-wave velocities, impedance contrasts and densities of the lithosphere in the New Madrid region and synthesized these results into a single model that can be used in earthquake simulations.
The region covers an area of approximately 600,000 km2 from Little Rock, Arkansas across to Nashville Tennessee, up to St Louis, Missouri. The model has currently been gridded at 3 km lateral resolution and from 5-m resolution near the surface to 10-km resolution at 100 km depth.