A statewide surface fault creep model for California derived from ARIA Sentinel-1 standard product interferograms

Gareth J. Funning, Simran S. Sangha, Marin Govorcin, & David Bekaert

Published September 10, 2023, SCEC Contribution #13224, 2023 SCEC Annual Meeting Poster #063 (PDF)

Fault creep – aseismic slip of faults in the brittle uppermost crust – is an important factor in assessing seismic hazards. The presence of creep on faults can reduce the amount of strain that accumulates on them that may drive future earthquakes, and may imply a frictional style that disfavors fault rupture in earthquakes.

The plate boundary zone in California is home to multiple strike-slip faults that exhibit creep. Here we present a first statewide InSAR-derived model of fault creep for the state produced using a uniform dataset and methodology. We use over 2300 standard Sentinel-1 Geocoded UNWrapped interferogram (GUNW) products from 9 Sentinel-1 tracks produced by the Advanced Rapid Imaging and Analysis (ARIA) Center for Natural Hazards project from the period 2014-2020. These are stitched together using the open-source ARIA-tools software, and inverted to produce InSAR time series and velocity maps with the open-source MintPy software. Tropospheric noise is corrected using the GACOS service. We take strike-perpendicular profiles of our InSAR velocity data every 2 km along mapped Holocene active faults in California, and estimate ascending and descending velocity offsets across the fault for each one. We use these to invert for the fault-parallel offset rates (i.e. creep rates) and vertical surface offset rates for each profile, excluding sites that may be affected by nontectonic motions, such as groundwater hydrology or subsidence.

Our completed fault map covers 56 major strike-slip fault segments, 14 of which show robust indications of creep. Examples include creep along over 80% of the surface trace of the Maacama fault, creep at rates of 2-6 mm/yr along the Coachella segment of the San Andreas fault, creeping areas on the Concord-Green Valley-Hunting Creek fault, and the expected large amplitude creep signals on the central San Andreas, Calaveras and Hayward faults. In contrast, major faults such as the Garlock, Elsinore, Newport-Inglewood and the Eastern California shear zone faults, and the rupture zones of the 1857 and 1906 earthquakes on the San Andreas fault, show no significant creep.

Key Words
fault creep, InSAR

Citation
Funning, G. J., Sangha, S. S., Govorcin, M., & Bekaert, D. (2023, 09). A statewide surface fault creep model for California derived from ARIA Sentinel-1 standard product interferograms. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy