Current status and future plans for the Community Geodetic Model (GNSS) products

Michael Floyd, Thomas A. Herring, Zheng-Kang Shen, Jessica R. Murray, William C. Hammond, & Mark Murray

Published August 15, 2020, SCEC Contribution #10668, 2020 SCEC Annual Meeting Poster #170 (PDF)

The Community Geodetic Model (CGM; https://www.scec.org/research/cgm) provides two sets of geodetic products, using GNSS and InSAR, and will ultimately provide a combined geodetic velocity field over southern California for use by the earthquake science community for a variety of applications. The GNSS and InSAR data allow for high temporal and spatial resolution, respectively, to constrain surface deformation associated with earthquake cycle processes, long-term tectonics, hydrologic cycles, geothermal features and other processes.

The GNSS products are derived from a combination of publicly available time series from operational analysis centers including GAGE (UNAVCO), Nevada Geodetic Laboratory (University of Nevada, Reno), NASA MEaSUREs (JPL and SOPAC) and the U.S. Geological Survey; we also provide an update of survey-mode GNSS products, which were previously released as part of the SCEC Community Motion Model. The consensus product ensures that any systematic differences due to each center’s chosen operational processing strategy and software are reduced by reweighting daily position uncertainties, averaging and expressing in an identical reference frame. We also build a consensus list of discontinuities, due to earthquakes and equipment changes, and other time series perturbations when fitting the consensus time series to produce estimates of tectonic velocities and other signals. Ultimately, these time series will be combined with the InSAR line-of-sight time series to produce the Community Geodetic Model, relative to which anomalous transient behavior may be identified and studied.

Here we present the workflow for combining GNSS products to make the CGM up until the mid-2019 Ridgecrest earthquakes. We also present a preliminary version of the CGM web viewer, which is currently under development at SCEC for search and dissemination of the CGM products. Future work will involve the combination of these products with the accompanying InSAR time series and velocities to form a self-consistent set of geodetic products, with a best-fit long-term tectonic model derived from geodesy.

Key Words
CGM, GNSS

Citation
Floyd, M., Herring, T. A., Shen, Z., Murray, J. R., Hammond, W. C., & Murray, M. (2020, 08). Current status and future plans for the Community Geodetic Model (GNSS) products. Poster Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
SCEC Community Models (CXM)