Active Normal Fault Segmentation and Linkage in the Umbria‐Marche Apennines (Italy): Insights From 3D Structural Modeling

Normal‐fault growth, segmentation, and their relationships with crustal inheritance and rheological layering are investigated in a post‐thrusting setting of the southern sector of the Northern Apennines. We integrate 3D modeling with gravity, thermal, and seismological constraints to reconstruct the geometry and evolution of the main normal fault systems in the study area, including that responsible for the 2016–2017 central Italy earthquake sequence. Our results support a crustal extensional system in which fault growth and seismogenesis are controlled by progressive segment linkage and structural inheritance, as well as rheological and thermal layering. The normal fault network is dominated by NW‐ to NNW‐striking, high‐angle segments that offset the pre‐existing thrust stack and propagate through the upper crust. Cumulative throw profiles and displacement‐length scaling are consistent with segment interaction and linkage, and strain localization within a mechanically layered crust. Cross‐cutting relationships indicate limited, non‐systematic reactivation of pre‐existing thrust surfaces, while the spatial arrangement of recent faulting suggests localization within crustal domains inherited from the Mesozoic rift template. Projecting earthquake hypocenters onto a new gravity‐constrained balanced geological section provides an unprecedented level of detail on seismicity distribution in the Apennines. Earthquake hypocenters are concentrated between ∼3 and ∼12 km depth and broadly overlap the levels occupied by the Upper Triassic dolomite‐anhydrite succession of the Burano Formation and Mesozoic carbonates lying in the footwall of the main thrust of the region (i.e., the Monti Sibillini Thrust); the vertical distribution of seismicity further reflects rheological contrasts involving a weak phyllitic interval overlying rigid crystalline basement.