Evaluation of the seismogenic potential in key areas of the central and southern Apennines through analysis of speleothem vulnerability

We used speleothem vulnerability for assessing the seismic ground shaking threshold probably experienced or not in caves located within Apennines seismogenic areas. On the southern flank of the Pollino Range, which is considered a current seismic gap, cave observations suggest the lack of significant earthquake-related deformation in the last 5-7 ka, but the widespread occurrence of creep. In the central Apennines, homogenously-trending collapses within the Grotta Cola (Petrella Liri, AQ) evidence a significant co-seismic deformation event radiometrically bracketed at 4-5 ka. We supplemented the cave observations with numerical modeling and static test analysis of the speleothem mechanical behaviour to stipulate probability density functions for the bending stress leading to rupture, and established different vulnerability curves for speleothems according to their shapes. Model results are consistent with the co-seismic deformation at Grotta Cola as being caused by the Liri or by the Velino fault. On the other hand, unbroken speleothems in the Pollino area were used to define an upper limit of the “strength” for earthquakes that could have occurred during the speleothems’ lifetime.