SCEC Award Number 17052 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Development of merged GPS time series for the Community Geodetic Model
Investigator(s)
Name Organization
Thomas Herring Massachusetts Institute of Technology Michael Floyd Massachusetts Institute of Technology
Other Participants
SCEC Priorities 1a, 2a, 3e SCEC Groups Geodesy, CXM, SDOT
Report Due Date 06/15/2018 Date Report Submitted 06/15/2018
Project Abstract
 We have generated initial combined time series analysis for the continuously operating GPS sites that will form the basis of and be distributed as part of GPS component of the SCEC Community Geodetic Model (CGM). We investigate techniques for the accurate and consistent recovery of secular velocities using a combination of time series from different analysis centers that make their products available for this purpose in the presence of time-dependent deformation, such as post-seismic decays. We have determined the weighting of individual contributions and transformed, though network rotation and translation, each of the input analyses into a common reference frame. The time series in this common reference frame are then averaged to generate the CGM GPS time series. These combined and individual time series have been available to the CGM participants for further analysis and for merging with InSAR times series. With additional software updates, we will be able to include even more analyses and when the reference frame scale effects are taken into account, consistent height estimates will also be generated.
Intellectual Merit This work is a core piece of the production of the GPS component of the SCEC Community Geodetic Model. This product will eventually act as a resource for both the scientific and wider public community. Consensus for creation of time series and crustal velocities is required due to the current variety of projects that generate relevant products through a variety of approaches, which may result in subtle but significant differences in interpretation.
Broader Impacts Geodetic data products are now incorporated into probabilistic seismic hazard analyses (PSHAs), and the accuracy of these relies on an accurate, widespread and dense fault displacement and crustal velocity estimates. Beyond the scientific use of these PSHAs, they form a part of community education and outreach products, where they are visualized for public consumption.
Exemplary Figure Figure 2
Caption for stand alone figure
North and East component residuals after removing a linear trends of 10.63 mm/yr and -7.11 mm/yr respectively for site P302 from the analyses of the centers whose time series results are being combined for the Community Geodetic Model. The non-secular components of the changes in the north and east positions is largely common among the analyses although there are differences that need to be understood. These non-secular components show why the time series for the CGM are needed.