SCEC Community Geodetic Model (CGM)

Introduction

The Community Geodetic Model (CGM) provides velocities of the Earth’s surface over southern California using data from Global Navigation Satellite Systems (GNSS), which includes the Global Positioning System (GPS), and interferometric synthetic aperture radar (InSAR), both space-based geodetic observation techniques. The GNSS products provide high temporal resolution (nominally daily measurement points) in three dimensions at specific observation sites and the InSAR products provide high spatial resolution (up to one point per 30 m distance on the ground). Combined, they provide the ability to study crustal deformation over a wide range of distances and periods.

Please see https://www.scec.org/research/cgm for more information.

Model Version: CGM1

This is the first major release of the CGM (version 1) and is distributed as a zip-file. See the README.txt file in the top directory of the archive for information about the directory structure and contents of the entire zipped archive. Much of the SCEC4 activity was focused on the assembly of GPS and InSAR data sets for measuring secular motions, comparing geodetically inferred fault slip rates with geological rates based on paleoseismic studies (e.g. UCERF3) and using geodetic observations to detect and investigate transient deformation. The CGM1 is a time-independent set of products, consisting of velocities of the Earth's surface measured by GPS and InSAR, and derived horizontal velocity and strain rate fields interpolated from the geodetic data using a variety of methodologies. The preferred, average (mean) fields and the individual contributions from participating researchers are included in this version.

Directory Structure and Contents

doc/

Documentation, containing a PDF of the technical report.

data/gps/

The CGM1 GPS horizontal velocity solutions in ASCII format (i.e. plain text), relative to the Stable North America Reference Frame. One header line in each file provides information about the data columns. These files correspond to those available from the former CGM "Horizontal GPS Velocities" web page.

data/grids/

The CGM1 grids of horizontal velocity and strain rate fields, derived from interpolation of the GPS velocity solutions, in netCDF format.

data/grids/contrib/

The CGM1 contributed grids of horizontal velocity and strain rate fields, from individual participating researchers, in netCDF format. These files correspond to those available from the former CGM "Model Comparisons" web page.

data/grids/mean/

The CGM1 preferred grids of mean horizontal velocity and strain rate fields (and associated standard deviations) in netCDF format. These files correspond to those available from the former CGM "Averages Horizontal Velocities and Strain Rates" web page.

data/insar/

The CGM1 InSAR line-of-sight velocity solutions, in ASCII (i.e. plain text) and netCDF format. These files correspond to those available from the former CGM "Line of Sight InSAR Velocities" web page.

data/insar/lindsey_los/

InSAR line-of-sight velocities in ASCII (i.e. plain text) format from Lindsey et al. (2015), doi:10.1002/2014JB011275. The included readme.txt file from the auxiliary material describes the content of the ASCII files. These files correspond to the contents of the "Southern San Andreas Compilation" tar-file from the former CGM "Line of Sight InSAR Velocities" web page. The full-resolution netCDF files are also provided and a script, make_ascii.com, samples and converts those netCDF files to the ASCII files using GMT's grdtrack.

data/insar/tong_los/

InSAR line-of-sight velocities in ASCII (i.e. plain text) format from Tong et al. (2013), doi:10.1029/2012JB009442. The included readme.txt file from the auxiliary material describes the content of the ASCII files. These files correspond to the contents of the "ALOS-1 Ascending" tar-file from the former CGM "Line of Sight InSAR Velocities" web page.

plots/grids/contrib/

PDF files showing the components of the contributed horizontal velocity fields, strain rate tensor and second invariant of the strain rate tensor from individual participating researchers.

plots/grids/mean/

PDF files showing the components of the mean horizontal velocity field, strain rate tensor and second invariant (and associated standard deviation) of the strain rate tensor.