The distribution of shallow creep on active faults in California, from a deformation velocity field derived from Sentinel-1 ARIA standard product interferograms

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

Published August 16, 2021, SCEC Contribution #11649, 2021 SCEC Annual Meeting Poster #102

The launch of Sentinel-1A in 2014 heralded an era of temporally dense SAR data coverage over tectonically active areas, such as the plate boundary fault system in California. The JPL/Caltech ARIA system is an effort to operationalize InSAR processing of this data stream, and produce standardized interferometric products that end-users can use for data exploration and analysis without the need to process the data themselves. This represents a savings of several orders of magnitude in computation time, bandwidth and data storage for end-users.

We demonstrate the utility of ARIA standard product data for geophysical analysis by using them to map fault creep on the major faults of California. First, we estimate the average surface deformation velocities for the region. Using the open-source software packages ARIA-tools and MintPy, we download, merge and crop over 2300 ARIA standard product interferograms from the nine Sentinel-1 tracks (five descending, four ascending) that cover California, and then invert the data from each track to estimate the corresponding average velocity field, using a Small Baseline Subset (SBAS) algorithm. Next, we take regularly-spaced, short-aperture, fault-perpendicular profiles through the velocity data along each major active fault, estimate the line-of-sight velocity offsets for each profile in both ascending and descending geometries, and invert these to estimate cross-fault relative vertical offset rates and fault-parallel offset rates (i.e. creep rates). Our InSAR-based estimates of shallow creep rates of up to 27 mm/yr for the central San Andreas fault broadly agree with spot estimates of creep rate from GNSS and alignment arrays, but also approximately treble the density of coverage along the whole creeping segment, allowing finer discrimination of spatial fluctuations of creep rate.

Key Words
fault creep, InSAR

Citation
Sangha, S. S., Funning, G. J., & Bekaert, D. (2021, 08). The distribution of shallow creep on active faults in California, from a deformation velocity field derived from Sentinel-1 ARIA standard product interferograms. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy