Studying Interseismic Deformation Using InSAR Phase-gradient Stacking: Application to the North Anatolian Fault

The geodetic measurements of accumulated strains along active faults during their interseismic periods have a strong connection with faulting dynamics and seismic hazards evaluation. InSAR has been widely applied to study the interseismic deformation along active strike-slip faults around the world. However, various limitations such as that from phase unwrapping errors and tropospheric delays are often encountered, hindering our interpretation and model inversion. Phase-gradient stacking is a method that sums up wrapped phase differences of adjacent pixels in multi-interferograms. It has been successfully conducted to reveal local deformation signals across coseismic fractures, yet lacks of application to relatively larger-scale deformation signals. Here we apply the phase-gradient stacking method, for the first time, to study the interseismic deformation along the North Anatolian Fault with Sentinel-1 SAR images acquired from 2014 to 2021. We obtain the strain rate field across the North Anatolian fault without the need of unwrapping hundreds of large interferograms. Segments with surface creep and strong coupling effects can be clearly distinguished in the phase gradient maps, allowing us to directly invert for their long-term slip rates and locking depths. Our preliminary, but promising results show that the phase-gradient stacking method has advantages in studying interseismic deformation along strike-slip faults by directly connecting strain with fault parameters.