3-D Geologic and Seismic Velocity Models of the San Francisco Bay Region Documentation
Bounding boxes of the models
Bounding boxes of detailed and regional (extended) velocity model regions. Gray lines denote major roads and white lines delineate major faults.
The detailed model is surrounded by the regional (extended) model to permit capturing large length scale features of seismic wave propagation along the northern San Andreas fault outside the domain of the detailed model. In the regional model details away from the San Andreas fault are grossly generalized in places. The regional model fits around the detailed model so it does not include the region covered by the detailed model.
The detailed and regional velocity models are rectangular volumes in a Transverse Mercator (TM) projection with the following parameters:
- Scale factor for central meridian: 0.99960000
- Longitude of central meridian: -123.00000
- Latitude of origin: 35.00000
- False easting: 0.00000
- False northing: 0.00000
- Azimuths of sides: 53.638, 323.638
KML file with bounding boxes.
Coordinates are WGS84 longitude/latitude. Models extend from sea level or top of ground surface down to 45 km below sea level. The model includes the material properties of water for the Pacific Ocean.
| Detailed | Regional (Extended) | |||
|---|---|---|---|---|
| Approx. Dimensions | 290km | 140km | 650km | 330km |
| SE corner (lon,lat) | -120.644051 | 37.050062 | -118.944514 | 36.702176 |
| SW corner (lon,lat) | -121.922036 | 36.320331 | -121.930857 | 35.009018 |
| NW corner (lon,lat) | -123.858493 | 38.424179 | -126.353173 | 39.680558 |
| NE corner (lon,lat) | -122.562365 | 39.174505 | -123.273199 | 41.484869 |
Geologic Block Model
Introduction
The detailed and regional (extended) 3-D geologic models of Central California, centered on the San Francisco Bay region, were made using the Dynamic Graphics EarthVision(TM) software. This program builds 3-D models starting with a hierarchy of fault surfaces that divide the volume of interest into Fault Blocks. These fault blocks are further subdivided by Zone Surfaces that most commonly represent contacts between rock units within a fault block.
Fault and zone surfaces were exported from the EarthVision (EV) model using an EV utility named "ev_ev2gocad", which outputs a file in the TSurf format used by the GOCAD(TM) software. The TSurf format represents a surface by specifying the locations a number of triangles which approximate the surface.
Various options for viewing TSurf files may be found under "Tools" on the SCEC Community Fault Model website. There are also scripts available in the tarball to project the tsurfs and to convert the projected versions to the .vtp format for viewing in the ParaView 3-D visualization software.
Documentation
- Slices through the detailed model
- Fault block hierarchy
- Text file of detailed model block and zone labels
- Text file of regional model block and zone labels
- Version history
Seismic Velocity Model
Introduction
The velocity model is stored in Etree database files. We provide a library to query the database from C++, C, and Fortran 77. The query software is called cencalvm (current version is 0.6.5) and is generally updated independently of the velocity model. In order to use the seismic velocity model, you need to download the Etree database file for the detailed model and install the query software. Downloading the Etree database file for the regional (extended) model is optional.
Documentation
- Query software
- Version history
- Detailed model
Elevation1 Horiz. Resolution Vertical Resolution z > -400m 100m 25m -400m > z > -3200m 200m 50m -3200m > z > -6400m 400m 100m -6400m > z > -45000m 800m 200m - Transition from detailed model to extended model. This is
a region 3.2km in width surrounding the detailed model. It is
part of the extended model.
Elevation1 Horiz. Resolution Vertical Resolution z > -3200m 200m 50m -3200m > z > -6400m 400m 100m -6400m > z > -45000m 800m 200m - Extended model
Elevation1 Horiz. Resolution Vertical Resolution z > -6400m 400m 100m -6400m > z > -45000m 800m 200m
