Imaging land subsidence and slow slip transients by combining InSAR and GNSS

SAR and GNSS are two dominant techniques to measure the Earth's deformation. They have different characteristics in that InSAR has superior spatial resolution, and GNSS has superior temporal resolution. Also, GNSS has better precision than InSAR, and InSAR measurements have significant spatial correlation mainly because of the atmospheric disturbance. Therefore, if available, InSAR measurements will be more precise when combined with GNSS measurements. This study investigates the temporal evolution of land subsidence and slow slip transients in the Boso Peninsula, Japan, from InSAR and GNSS measurements. First, we generated interferograms of available ALOS-2 images. The generated interferograms are corrected to be consistent with GNSS measurements every 20 km or so. The correction assumes that the spatial variation of the noise in InSAR measurements is represented as a polynomial function, the degree of which is constrained adaptively. Then, the corrected interferograms are fed to the time-series analysis. The time series generated allows us to separate continuing subsidence of up to 20 mm/yr with a shorter wavelength and slow slip transients with a longer wavelength.