Paleoseismological constraints on fault linkage and segmentation in the Cinque Miglia–Aremogna fault system, central Italy

We analysed the geological and structural setting, and paleoseismological record of the Aremogna–Cinque Miglia Fault System (ACMFS), located in the southernmost portion of the active extensional belt of the central Apennines (Italy). A key objective of the study was to test whether the ACMFS may have ruptured synchronously with the Mt. Morrone Fault to the north, for which previous work suggested rupture lengths exceeding 21 km to account for the displacements observed in paleoseismic trenches. We also examined the possible southeastward continuation of the system along the Ortona–Roccamonfina transverse lineament (ORL), which marks the boundary between the central and southern Apennine arcs, to assess whether inherited contractional structures may act as segmentation barriers. Geological and structural mapping, integrated with three paleoseismological trenches across the ACMFS, revealed evidence of at least four Holocene surface-rupturing earthquakes (younger than 3365 BCE). At least one of these events displays an age consistent with a surface-rupturing event recognized along the Mt. Morrone Fault. This temporal overlap suggests a possible “multi-fault system earthquake” involving both structures. On the other hand, the new surface and subsurface geological constraints appear to exclude the “physical continuation” of the ACMFS southeast of the ORL, suggesting that strain is instead accommodated by distinct fault architectures and deformation styles. This supports the view of the ORL as a major structural segmentation boundary.