Model Specific Notes
CVM names and naming conventions within UCVM can be confusing, largely because the CVM model names and abbreviations have changed during UCVM development, and there is not consistent use throughout the software and documentation.
UCVM users need to know the velocity model of interest, and then the abbreviation that UCVM uses to refer to the CVM of interest. The following tables briefly describes the standard CVM models available through UCVM, and the abbreviation used by the UCVM software to refer to each model.
UCVM is designed to present a standard interface to a variety of veloicty models. The fact that the models have quite different characteristics may introduce unexpected results for some applications. In the sections below, we try to describe unique characteristics of the each velocity model, to help users avoid mis-interpreting results from UCVM.
A KML file that can display the UCVM model regions is avialable here:
The velocity models registered into UCVM have been developed independently and they differ in many respects. UCVM tries to provide a standard interface to these models, which may facilitate comparisons between them. However, often detailed information about how the original models are defined and constructed is required to properly interpret the information provided by them.
The details about each model are typically provided in the associated peer reviewed publication. A list of these publications is given in the UCVM README. The following section identifies issues that should be considered when interpretting a model and the properties returned by UCVM.
- Is the original model defined as a flat model, or does it include topography?
- What are the model volume dimensions, including the depth of the model. Does the model include a default background model, or does it return no data, when queried outside its defined region.
- What material properties (e.g. Vp, Vs, density) were determined by the developers, and which properties are scaled from the original properties.
- Is the model defined for a solid volume, or does it leave information undefined in parts of its defined volume?
- Does the model have its own query interface, and if so, does the original interface provide information that is not returned by the UCVM standard query interface.
- Is it reasonable to modify the surface properties of the model with a Vs30-based geotechnical layer algorithm, like the Ely/Jordan GTL method implemented in UCVM?
- Does the model have an optional Geotechnical layer, to restore low Vs values near the surface. If so, at what depth does the model merge the GTL values with the main model.
- If the model is defined on a discritized mesh, are the returned values interpolated?
- Are the material properties interpolated, or returned without interpolation?
Details about models are provided in their associated papers, and in the sections below. Additional model specific descriptions are included in the GTL-Testing part of this wiki, which include test plots that show specific test queries to determine how specific models behave through using various UCVM query options.
If you have cannot find the answers to these questions about specific UCVM models, please contact us at software@scec.org and we will try to help answer questions about speficic UCVM models, based on our experience working with the models registered into UCVM.
UCVM provides query by elevation and query by depth options. Query by depth is the default, and depth is a positive number below ground level. Query by elevation is relative to mean sea level, with positive above sea level and negative below sea level.
Digital elevations models are used to support the query by elevation capabilities. UCVM has an embedded digital elevation model (DEM) that is uses to determine the elevation of any given lat,lon. This include bathemetry information for off-shore points. In some case, including CVM-H, the CVM-H basins, Cencal, Imperial, and Coachella models, they provide their own digital elevation model. There can be slight differences between the UCVM DEM and the native DEM. This can lead to small discrpencies for queries returned by UCVM and the native model query interface.
ALBACORE model is unusual in that it defines the model with elevation on land, but queries off-shore are relative to sea level.
Models with query by elevation will typically return Vs=0 for regions that are below sea level, but above ground level, indicating that the query is in water.
UCVM defines a configuration file for each registered model. The model configuration files are collected in the installation directory in UCVM/model/model_abbreviation/model_name.conf (e.g. UCVM/model/1d/1d.conf)
Users can examine these .conf files to determine basic information about a model. In most cases, these model configuration files are static, and should not be modified by the user. In a few cases, such as bbp1d.conf file, there are user configuration options in the bbp1d.conf file (specifically a flag to specify whether the model should be delivered with interpolation).
The parameters that can be set in the ucvm.conf and in the model specific model.conf files typically include whether the model will including a Ely/Jordan GTL and whether the model will include a default background model.
The Ely/Jordan GTL can be added by modifying the model.conf file, or on the ucvm_query command line. These two methods of adding the GTL are equivalent. The depth at which the Vs30 values are merged into the models Vp and Vs values is dependent on the model. In some modeles, like CVM-H, the default merge depth is 350 meters. For other models including CCA, and CVMS5, these models are coarser, so the merge depth is 500m. Please note that the rho values are modified by the Ely/Jordan method, but they are not merged into the native model values smoothly. The Ely/Jordan values are just replaced by the original values at the merge depth.
Southern California Velocity Model developed by Harvard Structural Geology Group with optional geotechnical layer (abbr:cvmh)[1.6G]. This is the most recent version of a southern California velocity model developed by the Harvard structural geology group. More information about the CVM-H velocity model is available on a SCEC Website: SCEC Community Velocity Model - Harvard Website
CVM-H has its own digital elevation model and it was designed to query by elevation. The UCVM interface provides query by depth capabilities for this model.
CVM-H model properties are returned without interpolation. This means the vertical resolution of the model can be seen in vertical profiles are stair step-shaped changes in the Vs, Vp, and rho properties.
CVM-H default configuration is to provide no geotechnical layer, and no background model. These can be added by modifying the CVM-H parameters in the ucvm.conf file. If a GTL is added, it applies a Vs30 GTL and smooths it with the underlying CVM-H properties at 350m.
Southern California Velocity Model developed by SCEC, Caltech, USGS Group with geotechnical layer (abbr:cvms)[326Mb]. This is the best available version of the rule-based SCEC southern California velocity model. SCEC produced several iteration of this model from about 1995-2004. The later version are considered improvements on previous versions of the SCEC CVM models, so this replaces earlier version. The version available through UCVM contains all available code fixes that have been added to the model since its release in 2004.
This models provides two regions that define a geotechnical layer (GTL), the return low Vs values, in the top 350m. These are polygon regions, as shown in the coverage maps, that provide GTL information Los Angeles region and in the Salton Sea area.
More information about the SCEC CVM-S4 is available on a SCEC Website at: SCEC CVM-S4 Website
Tomography improved version of CVM-S4 with no geotechnical layer but has an optional Ely-Jordan GTL (abbr:cvms5) [1.2G]. This is a tomography improved model of the CVM-S4 model. The tomography was performed on a 500m x 500m x 500m resolution mesh for the full region. The results are delivered on this fairly low resolution mesh, with linear interpolation used to determine material properties between mesh points. The tomography used a minimum Vs value for the region at about 900m/s, so this model does not deliver any low (or realistic) Vs values, when the GTL flag is set gtl = off. When the flag is set gtl = on, UCVM will add the Ely-Jordan Vs30-based GTL into the top 500 meters which provide velocities down to half the Vs30 values for each point, which may be 150m/s in some areas.
# UTM Zone utm_zone = 11 # Model directory model_dir = s5 # GTL on or off? gtl = off # Number of cells in x, y, and z. nx = 1536 ny = 992 nz = 100 # Depth, in meters depth = 50000 depth_interval = 500 # Density scaling parameters p5 = -0.0024189659303912917 p4 = 0.015600987888334450 p3 = 0.051962399479341816 p2 = -0.51231936640441489 p1 = 1.2550758337054457 p0 = 1.2948318548300342 # Corners, in UTM projection. bottom_right_corner_e = 596013.92402056302 bottom_right_corner_n = 3368878.9393477398 bottom_left_corner_e = 10616.346941343043 bottom_left_corner_n = 3863137.9139448642 top_right_corner_e = 915108.80599173578 top_right_corner_n = 3746813.1405760832 top_left_corner_e = 329711.22891251586 top_left_corner_n = 4241072.1151732076
CVM-S4.26 with added geotechnical layer (abbr:cvmsi)[1.6Gb]. This is a version of the CVM-S4.26 model that combines the tomography improved CVM-S4.26 model with some elements of the CVM-S rule-based geotechnical layer in the top 350m. This provides more realistic low Vs values often wanted in 3D ground motion simulations in the Los Angeles Region. The algorithm used to combine the tomography mesh, and the geotechnical layer are defined the UCVM site.
USGS developed San Francisco and Central California velocity model (abbr:cencal) [17Mb]. Cencal v08.3.0. Cencal is The USGS 3-D Geologic and Seismic Velocity Models of the San Francisco Bay region. This model provide a three-dimensional view of the geologic structure and physical properties of the region down to a depth of 45 km (28 miles). Construction of this 3D Bay Area model was a joint effort of the USGS Earthquake Hazards Program and the USGS National Cooperative Geologic Mapping Program.
Computational research has shown that the 3-D structure of the earth has a significant impact on how strongly an earthquake is felt at different locations and on the duration of the shaking. Because seismic waves propagate through different rock types with differing speeds that depend on the rock properties, the waves can be reflected and refracted as they travel through various rock types. These effects need to be understood in order to predict the shaking in future large earthquakes.
The Cencal 3-D models combine 100 years of surface geologic mapping by the USGS, the California Geological Survey, and many other institutions together with decades of research into the seismic properties of the rocks in the Bay Area. Traditional two-dimensional geologic maps show only the distribution of rock units at Earth's surface.
The Cencal Seismic Velocity Model is defined in two files, formatted as etrees.
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Detailed model USGSBayAreaVM-08.3.0.etree.gz (1.6 GB) This is an Etree database file for inner, fine resolution model covering the San Francisco Bay area
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Regional model USGSBayAreaVMExt-08.3.0.etree.gz(1.1 GB) This is an Etree database file for outer, coarser resolution model. The model fits around the detailed model and extends the region covered by the model. If you are only interested in the volume covered by the detailed model, you do not need to download this model.
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Cencal Coverage Region
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
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Topography Support
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Native Model Resolution
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.
Elevation Horiz. Resolution Vertical Resolution (see elevation note) z > -3200m 200m 50m -3200m > z > -6400m 400m 100m -6400m > z > -45000m 800m 200m Extended model Elevation Horiz. Resolution Vertical Resolution (see elevation model) z > -6400m 400m 100m -6400m > z > -45000m 800m 200m Elevation is given with respect to mean sea level, so -400m corresponds to 400m below mean sea level.
- Native Projection: 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
- Model External Website https://earthquake.usgs.gov/data/3dgeologic/
Central California Area Velocity Model at iteration 6 with an optional Ely-Jordan GTL (abbr: cca) [9.2Gb]. This is a trilinearly interpolated version of the 6th iteration of Po Chen and En-Jui Lee's full 3D tomographic inversions of the central California region. The inversions were done on a 500m coarse mesh, however the trilinearly interpolation allows this model to be queried at arbitrary precision. The GTL flag is default to off. When the flag is set gtl = on, UCVM will add the Ely-Jordan Vs30-based GTL into the top 500 meters.
# UTM Zone utm_zone = 10 # Model directory model_dir = i06 # GTL on or off? gtl = off # Number of cells in x, y, and z. nx = 1024 ny = 896 nz = 100 # Depth, in meters depth = 50000 depth_interval = 500 # Density scaling parameters p5 = -0.0024189659303912917 p4 = 0.015600987888334450 p3 = 0.051962399479341816 p2 = -0.51231936640441489 p1 = 1.2550758337054457 p0 = 1.2948318548300342 # Corners, in UTM projection. top_left_corner_e = 503240.523120 top_left_corner_n = 4051863.829470 bottom_left_corner_e = 779032.901477 bottom_left_corner_n = 3699450.983449 top_right_corner_e = 906054.312483 top_right_corner_n = 4367099.140150 bottom_right_corner_e = 1181846.690839 bottom_right_corner_n = 4014686.294129 # Data Layout Parameters seek_axis = fast-X seek_direction = bottom-up
CyberShake Study 17.3 Central California Velocity Model with an optional Ely-Jordan GTL (abbr:cs173) [72Gb]. This model was removed from this release, due to it's large size and limited use, but can be accessed from earlier versions of UCVM. CyperShake Study 17.3 Central California Velocity Model. This is a 175m resolution mesh tiled from CCA06, CenCal, CVM-S4.26-M01 with 10km smoothing on each horizontal interface used in the CyberShake Study 17.3, a Central California Seismic Hazard Model. The GTL flag is default to off. When the flag is set, gtl = on, UCVM will add the Ely-Jordan Vs30-based GTL into the top 175 meters.
# UTM Zone utm_zone = 11 # Model directory model_dir = cs173 # GTL on or off? gtl = off # Number of cells in x, y, and z. nx = 3200 ny = 6960 nz = 288 # Depth, in meters depth = 50400 depth_interval = 175 bottom_left_corner_e = 548969.079292 bottom_left_corner_n = 3459243.769232 top_left_corner_e = -448610.671359 top_left_corner_n = 4157755.975881 bottom_right_corner_e = 870071.761707 bottom_right_corner_n = 3917825.705794 top_right_corner_e = -127508.133290 top_right_corner_n = 4616338.305196 # Seek method, fast-X or fast-Y seek_axis = fast-Y seek_direction = top-down
CyberShake Study 17.3 Central California Velocity Model integrated with Harvard group's Santa Maria and San Joaquin Basin Models with an optional Ely-Jordan GTL (abbr:cs173h) [72Gb]. This model was reemoved from this release, due to it's large size and limited use, but is available from previous version of the software. CyperShake Study 17.3 Central California Velocity Model integrated with Harvard group's Santa Maria and San Joaquin Basin Models. The GTL flag is default to off. When the flag is set, gtl = on, UCVM will add the Ely-Jordan Vs30-based GTL into the top 175 meters.
# UTM Zone utm_zone = 11 # Model directory model_dir = cs173h # GTL on or off? gtl = off # Number of cells in x, y, and z. nx = 3200 ny = 6960 nz = 288 # Depth, in meters depth = 50400 depth_interval = 175 bottom_left_corner_e = 548969.079292 bottom_left_corner_n = 3459243.769232 top_left_corner_e = -448610.671359 top_left_corner_n = 4157755.975881 bottom_right_corner_e = 870071.761707 bottom_right_corner_n = 3917825.705794 top_right_corner_e = -127508.133290 top_right_corner_n = 4616338.305196 # Seek method, fast-X or fast-Y seek_axis = fast-Y seek_direction = top-down
ALBACORE Southern California off-shore Velocity Model (abbr:albacore) [2.3Mb]. The ALBACORE model was developed using off-shore ocean bottom sensors. This model is unique that it is defined as query by depth on shore, but query by elevation off-shore. This means, if you query a point in the ocean, depth 0 is not 0 meters below ground level, but 0 meters below mean sea level. In this case, ALBACORE will return Vs=0 to indicate you are in water.
In addition, the ALBACORE model coverage region varies by depth. Many UCVM models are defined for a rectangular region, but the horizontal extent of the ALBACORE models varies by depth.
SSIP Imperial Valley Velocity Model developed by LSU (abbr:ivlsu) [1Mb]
SSIP Coachella Valley Velocity Model developed by LSU (abbr:cvlsu) [1Mb]
Wasatch Front Community Velocity Model(UTAH) (abbr:wfcvm) [50Mb]
The CVM-H Basin models are the same resolution and contain the same material properties found in the CVM-H v15.1 model. However, these basin models are delivered as standlalone models so they can be combined with background models more easily.
CVMH Los Angeles Basin Velocity Model | cvmhlabn | 1.6G
CVMH San Gabriel Valley Basin Velocity Model | cvmhsgbn | 1.4G
CVMH Ventura Basin Velocity Model | cvmhvbn | 1.5G
CVMH Inner Borderland Basin Velocity Model | cvmhibbn | 2.1G
CVMH Ridge Basin Velocity Model | cvmhrbn | 1.4G
CVMH San Bernardino Basin Velocity Model | cvmhsbbn | 1.3G
CVMH Santa Barbara Channel Basin Velocity Model | 1.6G
CVMH Santa Maria Basin Velocity Model | cvmhsmbn | 1.6G
CVMH Salton Trough Basin Velocity Model | cvmhstbn | 2.5G
Southern California regional 1D model based on Hadley-Kanamori model (abbr:1d) [8Kb]. This is the UCVM default background model. It is a modified Hadley-Kanamori 1d model develop for southern California. This model uses linear interpolation between layers.
# 1D Velocity Model configuration
#
# Vp is interpolated between layer n to n+1.
# Rho is derived from vp (./src/ucvm/ucvm_model_1d.c)
# Vs is derived from Vp and Rho (./src/ucvm/ucvm_model_1d.c)
#
version=Hadley-Kanamori 1D (CVM-S)
# Depth of model in layers
num_z=9
# Depth to start of layer (km)
depth_vals=1.0, 5.0, 6.0, 10.0, 15.5, 16.5, 22.0, 31.0, 33.0
# Vp at start of layer (km/s)
vp_vals=5.0, 5.5, 6.3, 6.3, 6.4, 6.7, 6.75, 6.8, 7.8
This model definition only gives Vp values. Vs and rho are scaled from this Vp. The rules UCVM uses to produce the Vs, and rho values are giving in the ../src/ucvm/ucvm_model_1d.c files mentioned in this configuration file.
An table from the original Hadley Kanamori paper, giving the original HK 1D model definition is posted on a SCEC website: Hadley Kanamori 1D model description
Los Angeles Region 1D model used in SCEC Broadband Platform (abbr:bbp1d) [1Kb]. The BBP1D model was originally constructed by R. Graves as a 1d model for the Northridge Region. It was developed by averaging velocity profiles from a series of site around the Los Angeles basin. The resulting model is used in the SCEC Broadband Platform when simulating regional Los Angeles area earthquakes. This model configuration file provides a user specified flag specifying whether linear interpolation is used for material properties between layers. By default, linear interpolation is used.
# Northridge Region 1D Velocity Model Configuration # # This 1D model was defined by Graves and Pitrarka # in Table 3 of their paper: doi: 10.1785/0120100057 # It is used in the SCEC Broadband Platform format # for Los Angeles area simulations. # # Name of model. version=Northridge Region 1D Velocity Profile # Number of layers. num_z=18 # Interpolation method. # Set interpolation=linear to turn on interpolation # Set interpolation=none to turn off interpolation interpolation=linear # Columns # Thickness (km) Vp (km/s) Vs(km/s) Density (gm/cm3) Qp Qs # Start of model. # --MODEL-- 0.0020 1.7000 0.4500 2.0000 45.0000 22.5000 0.0040 1.8000 0.6500 2.1000 65.0000 32.5000 0.0060 1.8000 0.8500 2.1000 85.0000 42.5000 0.0080 1.9000 0.9500 2.1000 95.0000 47.5000 0.0100 2.0000 1.1500 2.2000 115.0000 57.5000 0.0700 2.4000 1.2000 2.2000 120.0000 60.0000 0.2000 2.8000 1.4000 2.3000 140.0000 70.0000 0.2000 3.1000 1.6000 2.4000 160.0000 80.0000 0.2000 3.4000 1.8000 2.4500 180.0000 90.0000 0.3000 3.7000 2.1000 2.5000 210.0000 105.0000 2.0000 4.4000 2.4000 2.6000 240.0000 120.0000 2.0000 5.1000 2.8000 2.7000 280.0000 140.0000 1.0000 5.6000 3.1500 2.7500 315.0000 157.5000 5.0000 6.1500 3.6000 2.8250 360.0000 180.0000 5.0000 6.3200 3.6500 2.8500 365.0000 182.5000 5.0000 6.5500 3.7000 2.9000 370.0000 185.0000 10.0000 6.8000 3.8000 2.9500 380.0000 190.0000 999.0000 7.8000 4.5000 3.2000 450.0000 225.0000
The following SCEC website provides more information about this model. https://scec.usc.edu/scecpedia/BBP_1D_LA_Basin_Model BBP1D LA Basin 1D Model
To provide query by depth and query by elevation and Vs30 values for all models, UCVM provides a statewide topography and Vs30 model. This is constructed as an etree data structure that stores the topography and vs30 values. The topography data is provided by USGS DEM. The Vs30 data is provided by Thompson California Vs30 Model(2018/2022). For regions outside of California, the Vs30 values were derived from the Wald vs30 topography relationship. The regional specification for the UCVM topography and Vs30 etree are:
# UCVM model config file # Projection parameters for reference proj_str=+proj=aeqd +lat_0=36.0 +lon_0=-120.0 +x_0=0.0 +y_0=0.0 proj_origin=-129.75,40.75 proj_rot=55.0 proj_size=1800000.0,900000.0
Map shows coverage region for California CVMs registered into UCVM. 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)
