Slip history of the Magnola fault (Apennines, Central Italy) from 36Cl surface exposure dating: evidence for strong earthquakes over the Holocene

To better understand the mechanics of deformation in the Mediterranean and the role that the convergence between Africa and Europe plays, it is necessary to know the deformation field at different time scales. Here we use in situ 36Cl surface exposure dating of exposed bedrock fault scarps to determine earthquake time-slip histories and to quantify slip rates over the last several thousand years. This information allows us to delineate the seismic history of normal faulting within the Mediterranean area over that time period. e studied the limestone scarp produced by the Magnola fault in the Central Apennines, Italy. The Magnola fault, in the Fucino area, is an active, 15-km long, normal fault striking WNW and dipping SSW. The range front morphology, characterised by steep triangular facets separated by V-shaped valleys and wine-glass canyons, suggests that the Magnola fault has been active for at least the last several hundred thousand years. At the base of the facets, the fault cuts limestone bedrock to produce a well-preserved normal fault scarp 10 to 12 m high. stribution of 36Cl concentration versus the height along that scarp is best explained by a minimum of five and a maximum of seven successive earthquake exhumations, with slips varying between 1.5 and 3 m. An age of ∼5 ka at the base of the scarp and of ∼12 ka at the top yields a slip rate of ∼0.8 mm/year. The absence of any event on this fault during the last 5000 years suggests either that a future event is imminent on the Magnola fault or that the fault has entered a quiescent period with much longer recurrence time. Our study confirms that the Magnola fault scarp is post-glacial and supports the hypothesis that similar scarps in the Mediterranean are also post-glacial.