What Can Be Concluded About Seismic History From Broken and Unbroken Speleothems?

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

“…The use of speleotectonics for the recognition of paleoearthquakes is highly debated in the literature both because there are many possible breakdown causes that must be discounted (e.g., Gilli, 2005) and because the required conditions to break speleothems, in terms of speleothems vulnerability and seismic input, are still unclear (e.g., Cadorin et al, 2001;Lacave et al, 2004). On the other hand, peculiar features, recognized in many caves worldwide, have been often linked to earthquake damages (e.g., Postpischl et al, 1991;Ferranti et al, 1997;Lemeille et al, 1999;Delaby, 2001;Forti, 2001;Kagan et al, 2005;Šebela, 2008;Panno et al, 2009;Bábek et al, 2015;Méjean et al, 2015), although specific paleoearthquakes identified in caves have been rarely constrained by independent data outside caves (Becker et al, 2005).…”

“…Empirical relations and quantitative modeling linking dimensions of speleothems and peak ground accelerations are difficult to be applied for the dated stalagmite, as too high accelerations (PGA > 10 m s −2 ) would have been needed to break it (e.g., Cadorin et al, 2001;Lacave et al, 2004). The answer to this question can be found considering that these correlations do not take into account some parameters and conditions such as structural and chemical compositional variability, presence of pre-existing discontinuities and/or anomalies within the concretions, and seismic site response (e.g., Delaby, 2001;Kagan et al, 2005), which can significantly influence the mechanic behavior and the strength of the material.…”

“…From a general point of view, therefore, the Cavallone Cave is lacking intact long and thin speleothems. This raises questions because long and thin concretions are the first to be destroyed during an earthquake and it is generally accepted in the literature that soda straw damages are reliable indicators of coseismic shacking (e.g., Lacave et al, 2004;Becker et al, 2006). Moreover, ceiling collapses are widespread and corroborated by the presence of piles of collapsed materials in many points along the conduit.…”

“…Evidence of falls and collapses, moreover, shows that the cave underwent several sudden deformation events (probably of different origin) during its development. Nevertheless, for the Galleria della Devas- tazione branch earthquake-induced damages are difficult to be invoked as the main cause of its present-day configuration, since the strength of the seismic events would have to have been far greater to break such large concretions (e.g., Cadorin et al, 2001;Lacave et al, 2000Lacave et al, , 2004Lacave et al, , 2012. A strong influence, instead, could have been exerted by gravitational processes that possibly caused the floor to sink (Fig.…”

“…Some authors state that high accelerations are needed to break speleothems and that only thin and long concretions can be damaged following seismic shaking due to "reasonably" strong earthquake (3 m s −2 < PGA < 10 m s −2 ) (e.g., Cadorin et al, 2001;Lacave et al, 2000Lacave et al, , 2004Lacave et al, , 2012. Nevertheless, field evidence cannot be neglected and suggests that empirical mechanical relations are possibly lacking for considering some significant parameters and conditions (Delaby, 2001).…”