SCEC Award Number 22036 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Comprehensive comparison and analysis of GNSS products for the Community Geodetic Model
Investigator(s)
Name Organization
Michael Floyd Massachusetts Institute of Technology Thomas Herring Massachusetts Institute of Technology
Other Participants
SCEC Priorities 1a, 2a, 3e SCEC Groups Geodesy, CXM, SDOT
Report Due Date 03/15/2023 Date Report Submitted 12/01/2023
Project Abstract
 We report here two contributions to the Community Geodetic Model, one involving our work within the Community Geodetic Model (InSAR) Working Group and one involving collation and processing of post-Ridgecrest survey GNSS observations, as well as ongoing operational production of the GNSS time series for the Community Geodetic Model. We have developed a new method for deriving tropospheric delay corrections for InSAR from publicly available products, using an approach based on the one that is used to calculate a priori estimates for GNSS processing, in collaboration with Katherine Guns (UCSD) as part of SCEC Award 22020. We have ingested more semi-continuous and survey GNSS observations from the field around the Ridgecrest earthquake, provided by Gareth Funning (UC Riverside) as part of SCEC Award 22049, among others, to produce updated time series and snapshots of cumulative displacement over several post-earthquake periods. PI Floyd has also continued to attend meetings every two weeks with the CGM (InSAR) Working Group to help collaborate with and guide that component of the CGM.
Intellectual Merit This work contributes directly to two core objectives of SCEC: the Community Geodetic Model (CGM) and earthquake response, in this case post-Ridgecrest. Although our usual contributions are to the GNSS component of the CGM, we have also been focused on guiding and being regularly involved with the InSAR Working Group. Through those interactions, and our experience and knowledge with GNSS methodologies, we have regularly offered advice on approaches for correcting various aspects of InSAR time series, as they have been developed by the CGM (InSAR) Working Group, and we report on one particular example of tropospheric delay here. Also, our collaborative efforts with G. Funning (UC Riverside) to augment the continuous GNSS network surrounding the earthquake, with denser and closer measurements to the ruptures, have generated several new multi-year GNSS time series at survey sites, whose displacements over various time periods following the earthquake are reported here and will aid in modeling afterslip and other poroelastic or viscoelastic effects.
Broader Impacts Both the new method presented for a tropospheric delay correction for InSAR and the additional survey GNSS data surrounding the Ridgecrest ruptures will act to underpin others' work throughout the InSAR community and those modeling the aftermath of the Ridgecrest earthquakes.
Exemplary Figure Figure 3: Cumulative displacement vectors at continuous (red), UCR/UCSD (blue) surveys, reported on here, and NGL/UNR (magenta) GNSS stations over various time periods following the Ridgecrest earthquakes. These time periods generally coincide with episodic surveys conducted by Gareth Funning (UC Riverside). [Credit: M. Floyd (MIT)]