Toward measuring global ground motion with L-band InSAR data independently

We are entering the golden age of L-band SAR satellites. These L-band data usually have sufficient coherence even in challenging areas for shorter wavelength SAR data that are most commonly used now. In the meantime, methods or models have been developed over the years to correct for the various InSAR phase components that are not of interest. These have laid the foundations for measuring global ground motion with InSAR independently. To demonstrate this capability, we use state-of-the-art techniques to process nearly 10 years of ScanSAR data acquired by JAXA's ALOS-2 satellite in western US, where there are a variety of areas ranging from high coherence areas in southern California, mid coherence areas in northern California, and low coherence areas in Washington. In particular, the Cascadia subduction zone represents one of the most challenging areas for InSAR, where we can hardly obtain reliable measurements with C-band data. For both InSAR and ionospheric phase estimation workflows, we form all interferograms, which can help mitigate closure phase. It also enables robust and high precision ionosphere correction, which is critical to measuring large-scale motion with InSAR data. We do not rely on external measurements from GNSS. The results reveal various deformations associated with plate motions, San Andreas fault, Cascadia subduction zone, water pumping in central valley, and many others. The results are encouraging, showing the great potential of L-band InSAR in measuring global ground motion independently. The capability will be further improved by future L-band missions with enhanced performance such as NISAR.