Plain Language Summary
Seismic hazard models rely on accurate measurements of small
interseismic motion over large space on the Earth’s crust. Traditional
geodetic models based on Global Navigation Satellite System (GNSS) data
cannot resolve small scale deforming patterns, mainly due to expensive
and limited station deployment. Interferometric Synthetic Aperture Radar
(InSAR) has become the emerging tool for mapping the surface
deformation, with its advantages of low-cost and full-coverage. Yet
InSAR measurement, compared to GNSS, comes with larger bias from the
atmospheric noise, especially over length scales greater than 80 km.
Here we combined the two methods to resolve fine spatial scales and
achieve high accuracy. Our results are presented as deformation
time-series over the entire San Andreas fault system. From these
deformation time series we have estimated fault creep rates and strain
accumulation. One important finding is that there is significant
off-fault strain, though we suspect they are mainly due to hydrological
processes. These results will advance our knowledge of the earthquake
cycle, strain/moment accumulation, and the associated seismic hazards.