Abstract
Interferometric Synthetic Aperture Radar (InSAR) measurements are
increasingly being used to measure small amplitude tectonic deformations
over large spatial scales. Residual signals are often present at these
scales, and are interpreted to be noise of indeterminate origin,
limiting studies of long-wavelength deformation. Here, we demonstrate
the impact of bulk motion by the Earth’s tectonic plates on
InSAR-derived velocity fields. The range-dependent incidence angle of
the InSAR observations, coupled with plate velocities of centimeters per
year, can induce long-wavelength spatial gradients of millimeters per
year over hundreds of kilometers in InSAR-derived velocity fields. We
show that, after applying corrections, including for the ionosphere and
troposphere, plate motion represents the dominant source of
long-wavelength secular velocity gradients in multi-year time series for
several study areas. This signal can be accounted for using plate motion
models, allowing improved detection of regional tectonic strain at
continental scales.