Principal Investigator (PI): Yehuda Bock, University of California, San Diego

The data requirements for understanding earthquakes and the processes that drive tectonic motion and crustal deformation have evolved over the last decade in response to new theoretical insights gleaned from long-term daily displacement time series from continuous GPS networks. For example, the interseismic stage of the earthquake cycle was thought to be a secular process punctuated by sudden earthquakes and a period of postseismic relaxation. However, increasingly long and precise time series have revealed subtle changes in the interseismic period that include repeated transient slip such as earthquake tremor and slip (ETS) first discovered in Japan and Cascadia.

Furthermore, comparative studies of GPS velocity fields at different periods of the earthquake cycle, especially at subduction zones, indicate that “interseismic velocities” may vary in time. Both of these insights contribute to an improved understanding of the underlying physical processes. Furthermore, there is a community interest in high-rate GPS and complementary seismic data to better understand earthquake rupture, fault dynamics, and hazards mitigation. Other applications of interest include GPS meteorology, related climate studies, and InSAR calibration and environmental monitoring such as near-surface water content.

Our team at Scripps Institution of Oceanography (SIO) and the Jet Propulsion Laboratory has been a leader in continuous GPS through our collective research efforts, instrument development, data fusion, and Solid Earth Science ESDR product generation as part of MEaSUREs (Solid Earth Science ESDR System-2012), REASoN, ACCESS 2005 (Modeling and On-the-fly Solutions in Solid Earth Science), ACCESS 2015 (Deploying Technology for Distributed Use of Global Navigation Satellite System Products in Earthquake and Tsunami Warning), Advanced Information Systems Technology (AIST) Program, and Early Stage Innovations (ESI) projects.

We will build on our expertise and these NASA investments by continuing and extending the generation and archiving of mature geodetic products as part of the MEaSUREs SESES project and to provide a new set of multi-decade ESDRs

Our team will provide the following new multi-decade calibrated and validated geodetic-derived ESDRs:

  • Daily displacement time series, velocity vectors, coseismic and postseismic deformation.
  • Troposphere and precipitable water vapor time series.
  • High-rate seismogeodetic displacement and seismic velocity time series of large earthquake events.
  • Time series from additional high-quality GPS sites in regions of interest.
  • Transition to GNSS-based time series during the course of the project as the software tools for GNSS processing become available.

Our team proposes to provide the following new multi-decade calibrated and validated geodetic-derived ESDRs:

  • Continuous multi-year high-rate GNSS, seismogeodetic, and meteorological time series to support a more detailed examination of, for example, the transition from seismic to coseismic to early-postseismic motion, and atmospheric turbulence.
  • Catalog of transient deformation in tectonically areas known for aseismic motion such as ETS. Furthermore, we will add terms to model these effects so that residual time series can be mined for further signals of interest.
  • Continuous estimation and cataloging of total near-surface water content derived from continuous GNSS time series over the continental U.S.

All ESDRs will be accessible through NASA’s Archive of Space Geodesy Data, located at the Crustal Dynamics Data Information System (CDDIS) and at SIO, and through the project’s GPS Explorer web portal.

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