Billy James Andrews , Zoe K Mildon , Manuel-lukas Diercks, Sam Mitchell, Gerald Roberts, Constanza Rodriguez Piceda, Jennifer Robertson

Reliable kinematic (slip vector) data collected from offset piercing points, corrugations or striations, is a key input for fault based seismic hazard assessments. However, it can be difficult to interpret kinematic indicators on degraded fault scarps. In this work, we investigate the orientations and growth history of on-fault fracture networks, which extend into the footwall and have greater preservation potential, to test whether they can be used to infer slip vector. We identify various F-S lineation patterns preserved across eight faults in Italy (Central Apennines) and Greece (Perachora Peninsula), including sinistral, dextral, and parallel arrays. Our analysis reveals F-S lineations exhibit orientations that correlate with the measured slip vector, with kinematics of arrays related to slip-vector rake. Relative age relationships support a model of fracture growth where isolated en-echelon fractures evolve into interconnected networks during successive earthquakes, driven by footwall uplift and the intersection of a 3D strain ellipsoid with the fault plane. Further, we demonstrate F-S lineations and arrays may serve as reliable kinematic indicators, even on degraded fault scarps. Further analysis of on-fault fracture networks will enhance our understanding of earthquake dynamics, long-term fault behaviour, and may contribute to seismic hazard assessments through the identification of fault tips.