Characterization and Evolution of Seismic Sequences in the Normal Fault Environment of the Southern Apennines

The use of seismic catalogs enhanced through advanced detection techniques improves the understanding of earthquake processes by illuminating the geometry and mechanics of fault systems. In this study, we performed accurate hypocentral locations, source parameters estimation and stress release modeling from catalogs of microseismic sequences nucleating in the complex normal fault system of the Southern Apennines (Italy). The application of advanced location techniques resulted in the relocation of ∼30% of the earthquakes in the enhanced catalogs, with hypocenters clearly identifying local patches on kilometer-scale structures that feature consistent orientation with the main faults of the area. When mapping the stress change on the fault plane, the inter-event distance compared to the size of the events suggests that the dominant triggering mechanism within the sequences is static stress transfer. The distribution of events is not isotropic but dominantly aligned along the dip direction. These slip-dominated lineations could be associated with striations related to fault roughness and could map the boundary between locked and creeping domains in Apulian platform and basement.