The Impact of Plate Motions on Long‐Wavelength InSAR‐Derived Velocity Fields

• Published in: Geophysical research letters Vol. 49; no. 21
• Main Authors: Stephenson, Oliver L., Liu, Yuan‐Kai, Yunjun, Zhang, Simons, Mark, Rosen, Paul, Xu, Xiaohua
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.11.2022
• Subjects: Corrections; Deformation; Deformation effects; Earth; Earth motion; Earth surface; Fields; geodesy; Hydrology; Incidence angle; InSAR; Interferometric synthetic aperture radar; Interferometry; Ionosphere; long‐wavelength deformation; Motion perception; Movement; Plate motion; Plate tectonics; Plates (tectonics); Radar; reference frames; SAR (radar); Satellite imagery; Synthetic aperture radar; Synthetic aperture radar interferometry; Tectonics; Troposphere; Velocity; Velocity distribution; Velocity gradient; Velocity gradients; Wavelength
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL099835

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 rigid motion by the Earth's tectonic plates on velocity fields derived from InSAR. 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 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. Plain Language Summary Radar interferometry from repeat satellite images has been used to measure slow motions of the Earth's surface. These motions could help us understand a range of processes happening at and below the surface, from hydrology to tectonics. We show how the rigid motion of Earth's tectonic plates can create a ramp effect in InSAR data that may obscure long‐wavelength deformation signals of interest. We demonstrate a simple method for removing this ramp effect, making InSAR more useful for studying very small motions over large areas of the Earth, especially in regions where we do not have good observations from other sources. Key Points Rigid plate motions, coupled with line‐of‐sight variation, introduce long‐wavelength spatial gradients in Interferometric Synthetic Aperture Radar (InSAR)‐derived velocity maps Plate motion effects dominate the long‐wavelength components in InSAR velocities after ionospheric correction Plate motion effects can be easily accounted for using plate motion models, improving long‐wavelength deformation mapping from InSAR