Defining a Mid-Holocene earthquake through speleoseismological and independent data: constraints for the outer Central Apennines (Italy) seismotectonic framework

Abstract

Abstract. A speleoseismological study has been conducted in the Cavallone Cave, located in the easternmost carbonate sector of the Central Apennines (Maiella Massif), in a seismically active region interposed between the post-orogenic extensional domain, to the west, and the compressional one, to the east. The occurrence of active ''silent normal faults'', to the west, close to blind thrust, to the east, raises critical questions about the identification of the true seismogenic sources for this transitional zone. Large ceiling collapses, fractures, broken speleothems with new re-growing stalagmites on their top, preferential orientation of fallen stalagmites and absence of thin and long concretions have been observed in many portions of the conduit and may indicate that the cave suffered of sudden and catastrophic events likely linked to the occurrence of past strong earthquakes. Although controversies exist about the correlation between speleotectonic observations and quantitative modeling, speleotectonic studies, when corroborated by independent data collected outside caves, can play a fundamental role in discovering past earthquakes. Radiocarbon dating and, above all, the surprisingly correspondence with other coeval paleoseismological and geological data collected in surrounding areas outside the cave, provide important constraints for the individuation of a Mid-Holocene paleoearthquake around 4770 ± 30 yr BP and for the identification of the Sulmona normal fault as the most likely causative structure.