Poster #098, Tectonic Geodesy

Strain rate mapping along the San Andreas fault system with integrated InSAR and GNSS time-series

Xiaohua Xu, David T. Sandwell, Emilie Klein, & Yehuda Bock
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Poster Presentation

2021 SCEC Annual Meeting, Poster #098, SCEC Contribution #11094 VIEW PDF
Measuring crustal strain and seismic moment accumulation is crucial for understanding the growth and distribution of seismic hazards along major fault systems. In order to do that, it is important to acquire an accurate estimate of the present-day and continuous stage of crustal deformation. Here we develop a practical approach to integrate the first 4.5 years (2015 - 2019.5) of Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) and continuous Global Navigation Satellite System (GNSS) time series to achieve 6 to 12-day sampling of surface displacements at ~500 m spatial resolution over the entire San Andreas fault system (SAFS). We decompose the line-of-sight InSAR displacements int...o three dimensions by combining the deformation azimuth from a GNSS-derived interseismic fault model. We then construct strain rate maps using a smoothing interpolator with constraints from elasticity (gpsgridder). The resulting deformation field reveals a wide array of crustal deformation processes including: on- and off-fault, secular and transient tectonic deformation; creep rates on all the major faults; and vertical signals associated with hydrological processes. The strain rate maps show significant off-fault components that were not captured by GNSS-only models. These results are important in assessing the seismic hazard in the region, though challenges remain in splitting tectonic and hydrologic sources and whether hydrologic strain will increase seismic hazards.