High-Resolution Interseismic Strain Mapping From InSAR Phase-Gradient Stacking: Application to the North Anatolian Fault With Implications for the Non-Uniform Strain Distribution Related to Coseismic Slip Distribution

High-resolution interseismic strain mapping is important for studying faulting behavior and for assessing seismic hazards. Interferometric Synthetic Aperture Radar has been widely applied to measure interseismic deformation along active strike-slip faults. However, phase unwrapping errors and over-smoothing effects limit its ability to map the extremely-high strain due to shallow creep. Here, without the involvement of ground-based measurement, we perform phase-gradient stacking on wrapped Sentinel-1 interferograms to directly map the shear strain rates along the North Anatolian Fault (NAF) with unprecedented resolution. The derived high-resolution strain-rate map reveals five strain-concentrated segments on the NAF, implying shallow creeps. We find that their spatial distribution coincides with the lower coseismic slip of previous earthquakes that occurred since 1939. The proposed method can be applied to other less-studied strike-slip faults to distinguish segments with shallow creep and strong coupling, and thus to better quantify the shallow strain budget and its associated seismic hazards.