Oblique Plate Convergence and Strain Accumulation  in Northern Algeria from InSAR Analysis

This study investigates crustal deformation associated with moderate to large earthquakes along the Africa–Eurasia plate boundary in the western Mediterranean using Synthetic Aperture Radar interferometry (InSAR). We integrate multi-temporal Sentinel-1A/B SAR time series (MT-InSAR) with GPS measurements to obtain high-resolution deformation estimates in the central Tell Atlas of northern Algeria, a region characterized by significant seismicity driven by oblique plate convergence. A dataset of 120 Sentinel-1 C-band SAR images acquired between 2015 and 2023 from ascending and descending orbits was processed to capture deformation from multiple viewing geometries. Interferograms were selected using baseline thresholds to maximize coherence and detect subtle ground motion (< 5 mm/yr). Mean horizontal velocity profiles were modeled using a nonlinear least-squares inversion to estimate key fault parameters. The results indicate slip rates ranging from 3.5 to 6.0 mm/yr, with an average of ~5 mm/yr, and shallow fault locking depths (< 20 km). The deformation field reveals dominant E–W right-lateral motion and NNW–SSE contraction at rates of 2–3 mm/yr, consistent with transpressional tectonics associated with oblique convergence relative to the stable High Plateaus. These findings provide new constraints on strain accumulation and the long-term behavior of active faults, with important implications for seismic hazard assessment in northern Algeria.Keywords: MT-InSAR, GPS, Tell-Atlas, oblique convergence, seismic hazard