SCEC Award Number 15082 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Reprocessing and geophysical fingerprinting of vertical GPS time series in Southern California: Toward an integrated crustal deformation model
Investigator(s)
Name Organization
Adrian Borsa University of California, San Diego David Sandwell University of California, San Diego Duncan Agnew University of California, San Diego Thorsten Becker University of Southern California
Other Participants
SCEC Priorities 1d, 2d, 5b SCEC Groups Geodesy, SDOT, CME
Report Due Date 03/15/2016 Date Report Submitted 06/01/2016
Project Abstract
 This project aimed to 1) provide improved vertical crustal velocity estimates for California using improved meth- odologies for correcting GPS position time series for the effects of loading from terrestrial water, atmosphere and non-tidal ocean variations, as well as from transient coseismic displacements, and 2) interpret both horizontal and (improved) vertical velocities in the context of regional tectonics and mantle convection. We made several ad- vancements related to improving GPS vertical velocities, presented our findings on the need for combining satellite gravity data with GPS at the SCEC Annual Meeting, presented our observations about the limitations of current GPS time series at SCEC Community Geodetic Model workshop, and published the first of several planned papers linking mantle convection, seismicity and crustal deformation.
Intellectual Merit This project has supported the development of corrections to western USA vertical velocity estimates from GPS to account for loading-induced displacements from atmosphere, oceans and terrestrial water. Our realization of the need for an independent constraint on secular loading changes has prompted our integration of terrestrial water storage estimates from NASA's GRACE mission, a work currently in progress. We were also able to contribute our insights into the limitations of currently available GPS time series to the SCEC Community Geodetic Model working group.
Broader Impacts We have used our analysis of GPS time series from different analysis centers to engage in a dialogue with NSF's National Geodetic Facility (GAGE) about their processing procedures. GAGE's time series are used by many hun- dreds of users across academia, industry, the public sector, and education, and we think our discussions will be reflected in future academic and instructional materials that explain the GAGE methodology.
Exemplary Figure Figure 1. Trade-off between inferred hydrological loading change and vertical rate estimate. If the rate is estimated using the entire time series (left), the inferred loading change is small. If the rate is estimated through 2013 (right) to avoid bias from the large drought-induced uplift from 2013~2015, the loading change is large. Independent constraints from the GRACE mission will help partition long-term changes between hydrological and tectonic sources.