USGS GNSS data collection and analysis for quantifying interseismic fault creep and imaging slip throughout the earthquake cycle
Jessica R. Murray, Eleyne Phillips, & Ryan TurnerSubmitted August 30, 2026, SCEC Contribution #15099, 2026 SCEC Annual Meeting Poster #TBD
Creep is well-documented on several faults of the San Andreas system in northern California. Geodetic measurements of crustal deformation surrounding creeping faults are a primary observation for modeling the rates and spatial distribution of creep. This information, in turn, influences seismic hazard assessment by informing our understanding of moment deficit rates, earthquake rupture propagation, and the maximum earthquake magnitude a fault will likely produce. Measurements spanning multiple earthquake cycles on creeping faults like the San Andreas near Parkfield support the development of testable hypotheses regarding the role of aseismic slip in the earthquake cycle.
The USGS Earthquake Science Center has built a decades-long history of campaign-style Global Positioning System (GPS) measurements along creeping faults throughout northern California and the Parkfield region. This sustained effort has generated three-dimensional interseismic velocities at substantially denser spatial sampling than existing continuous Global Navigation Satellite System (GNSS) coverage along the Green Valley, Bartlett Springs, and Maacama faults, as well as the Parkfield and Cholame sections of the San Andreas. We also maintain 11 continuous GNSS stations in the Parkfield area that are well-positioned to observe creep and afterslip in the upper few kilometers of the fault. We have used these data sets, in conjunction with alignment array observations and GNSS data from other regional networks, to image the spatial distribution of creep on the Maacama and Bartlett Springs faults, as well as the relationship among interseismic creep, coseismic slip, and afterslip at Parkfield. The data produced by our GNSS monitoring program complement a growing body of InSAR data by recording deformation in three dimensions and, in the case of continuous stations, at 1 Hz temporal sampling.
Our current efforts are focused on hardening physical infrastructure and data acquisition for our continuous GNSS stations, maintaining targeted campaign GPS field deployments, ensuring robust availability of derived GNSS data products, and leveraging GNSS and other geodetic data acquired in recent years to update and refine creep models for Parkfield and elsewhere.
Key Words
fault creep, Parkfield
Citation
Murray, J. R., Phillips, E., & Turner, R. (2026, 08). USGS GNSS data collection and analysis for quantifying interseismic fault creep and imaging slip throughout the earthquake cycle. Poster Presentation at 2026 SCEC Annual Meeting.
Related Projects & Working Groups
Tectonic Geodesy
