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| Southern Californian Velocity Model |
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Who is working on this? In collaboration with:
Fig. 1: perspective view of horizontal section through CVM-H illustrating basin and background velocity structure. Large box for low resolution, small box for high resolution model. Full size JPEG here. |
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CVM-H The SCEC CVM-H (Suess and Shaw, 2003) describes the seismic p-wave velocity structure in the Los Angeles basin and surrounding areas, and provides calibrated relations between Vp, shear wave velocity (Vs), and density as described in Komatitsch et al., (1994) (BSSA, 94/1, pp. 187-206). Vp/Vs varies linearly from 1.732 in the deepest part of the basin (Poisson's ratio of 0.25 at a depth of 8.5 km) to 2 in the shallow sediments near the surface (Poisson's ratio of 0.3 at the surface). Based upon well-log information, density is defined by rho=Vp/3+1280 (McCulloh, 1960;Stidham et al.,2001), imposing a minimum of 2000 kg/m-3. No specific shear quality factor is predicted by the model. A Q of 90 has been used in the sediments by Komatitsch et al. (2004). The model is defined by two gridded volumes with higher and lower resolutions, as well as two surfaces used to define the volume of sediments (the top pre-cretaceous basement and topography/bathymetry). A water-layer with a vp- velocity of 1480 is included. No vs is defined for water, and density is 1000. |
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Fig. 2: detailed perspective views of topography/bathymetry, basement and sections in high resolution model. Full size JPEG here. |
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Referencing Use of this model should reference: The underlying tomographic model is taken from: |
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Location and Resolution The model was designed in a UTM Zone-11 projection with the following coordinates,for the lower resolution model: Origin(SW) : 283000 3655000 (-119.322991 / 33.013591) for the higher resolution model: Origin(NW) : 371053.25 3774000 (-118.397883 / 34.100621) |
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Fig. 3: location of low resolution (green box) and high resolution (yellow box) model and regional sections. Full size picture available here. |
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Fig. 4: perspective view of contoured, complex basement surface and serial section through high resolution model. Full size picture available here. |
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File Format The velocity volumes are stored in the GoCAD voxet format. Please refer to the provided README that comes with the sources for further questions.
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Downloads: To download, right click on the file, and choose "save link as..." The latest available files can be found tarred and zipped as vx53.tar.bz2 (~186MB) Descriptions of both formats: The velocity files are stored in Voxet format. The topography/bathymetry and top basement horizons are represented as triangulated surfaces in the GoCAD tsurf format. A detailed description of both formats can be found within the guide here.
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