InSAR-derived finite fault modeling of the small-magnitude (ML 4.4) 2023 Umbertide earthquake (central Italy)

The 2023 M L 4.4 Umbertide extensional earthquake in Central Italy provides a valuable opportunity to test the capability of Differential Interferometric Synthetic Aperture Radar (DInSAR) to detect surface deformation associated with small earthquakes (M < 5). In this work, we invert Sentinel-1 displacement maps from the European Plate Observing System (EPOS) platform to investigate the possible source. We perform a linear Bayesian static slip inversion of DInSAR line-of-sight data, constraining the fault geometry using the nodal planes and the new relocated mainshock. The results suggest the activation of the NE-dipping splay of the Alto Tiberina Fault, consistent with the relocated aftershock distribution. The deformation component, obtained by combining multiple line-of-sight displacement maps, corresponds to 2 cm of vertical and 1.5 cm of eastward horizontal deformation and further supports the NE-dipping solution. This work demonstrates the capability of an integrated InSAR-based approach to detect weak deformation and model frequent small-magnitude earthquakes in high seismogenic potential areas.