SCEC Award Number 25202 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Spatiotemporal interpolation and correction of perturbations in GNSS time series and velocity products for the Community Geodetic Model
Investigator(s)
Name Organization
Michael Floyd Massachusetts Institute of Technology Thomas Herring Massachusetts Institute of Technology
SCEC Milestones A1-1, A3-5, A3-6 SCEC Groups Geodesy, CEM, SDOT
Report Due Date 03/15/2026 Date Report Submitted 05/07/2026
Project Abstract
 We propose to investigate methods for interpolating geodetic (GNSS) time series in time and velocities in space using colocation approaches. Both have multiple possible uses. Time series interpolation by considering spatial covariances may be used to fill in gaps where continuous data are necessary, such as when employing principal or independent component analysis (PCA or ICA, respectively) and also for constraining periods where little data exist or are otherwise not constrained by enough data before an event, such as the perturbation in estimated "interseismic" velocities around the 1992 Landers earthquake. The spatial output of such work can be also be used as a contributing solution to the Community Velocity Field Exercise proposed for to take the CGM from its current GNSS and InSAR time series and velocity products to model velocity and strain rate fields. We also propose to continue to vet the incoming sources from publicly available analysis centers which are ingested into the CGM, since we have uncovered some clear examples of gross errors which adversely affect the CGM (GNSS) combination technique as it currently operates. This is a natural extension of work we have contributed in previous years, which is to understand, correct, align and combine all available sources of continuous and survey GNSS data throughout the SCEC region to provide the most comprehensive set of GNSS time series and velocity products for the community.
SCEC Community Models Used Community Geodetic Model (CGM)
Usage Description The results presented here contribute to the Community Geodetic Model rather than using it.
Intellectual Merit The rigorous, consistent and regular update of geodetic velocity solutions, specifically a combination of continuous and survey GNSS velocities from several publicly available and commonly used sources here, is critical for input to provide constraints on seismic hazard assessments, such as updates of the the National Seismic Hazard Model. Geodetic constraints also provide surface measurements which must be explained by parameters in other crustal models, such as stress, rheology and temperature. The Community Geodetic Model (CGM) therefore provides critical observations within the suite of Community Earth Models (CEMs).
Broader Impacts Dense geodetic solutions and derived fields are one of the few direct observations of the displacement of Earth's surface. Therefore continued and, in the aftermath of an earthquake, rapid geodetic measurements provide information on where and how fast the crust is moving, leading to identification of unknown faults, constraints on known faults and localized monitoring of post-earthquake perturbations to the background tectonics for seismic hazard assessment and mitigation. The research done during this project inform similar larger-scale (nationwide) exercises, through our involvement with the National Geophysical Facility, for example as a contribution to the USGS's National Seismic Hazard Models.
Project Participants M. Floyd (MIT) compiled the latest velocity solution. T. Herring (MIT) produced the strain rate field by colocation. We downloaded and used publicly available GNSS products from several sources, including from the National Geophysical Facility, operated by EarthScope (formerly GAGE); the Nevada Geodetic Laboratory at the University of Nevada, Reno; the NASA Jet Propulsion Laboratory and Scripps Orbital and Permanent Array Center contributions to the ESESES MEaSUREs project; the National Geodetic Survey's multi-Year CORS Solution 3 (MYCS3) for the NOAA CORS Network; the U.S. Geological Survey; and Zheng-Kang Shen's processing of SCEC survey GNSS data (e.g. SCEC Award Number 20182).
Exemplary Figure Figure 2: Spatially interpolated strain rate by colocation of an updated combined velocity solution of continuous and survey GNSS data from several publicly available analysis center sources. (T. Herring and M. Floyd, MIT)
Linked Publications

Add missing publication or edit citation shown. Enter the SCEC project ID to link publication.