Dating earthquake damage of the Modena cathedral vaults (Northern Italy): an integrated approach

The medieval Modena cathedral (Northern Italy) was modified in the 15th century with the construction of 23 new vaults, which were progressively added throughout. A detailed survey of the vaults binder revealed the scars of multiple repair works after several earthquakes, resulting in a complex patchwork of lime mortar repairs over original gypsum vaults and gypsum repairs over original lime vaults. No apparent systematic construction criteria were followed to dictate the use of lime or gypsum binders. We used an integrated approach based on different absolute dating techniques in order to clarify the original vaults construction timing and to define the chronology of the restorations. The aim was to correlate the main restoration works to the earthquake chronology deduced from the catalogue of historic earthquakes. Radiocarbon dating using sequential dissolution (Lindroos et al., 2018) and Optically Stimulated Luminescence of the sand aggregate (Panzeri et al., 2018) were carried out to date the lime mortars and Thermoluminescence to date bricks. The preliminary results suggest that lime mortar was used both as original building material and for later major repairs. Some vaults were entirely rebuilt using a gypsum binder, and some others originally built using lime mortars were modified at least two times using two different gypsum mortars. These results are particularly significant because we were able to demonstrate that the vaults suffered much larger damage induced by earthquakes than previously assessed just by mapping fracture and crack networks.