Defining the causes of ancient building collapse (structural decaying vs. seismic shaking) in archaeological deposits of central Italy

Abstract

Deposits that result from the collapse of buildings are usual in geoarchaeological records. Deposition can result from natural processes or can be induced by human actions. The investigations at archaeological sites (in particular of the Roman Imperial Age) in central Italy indicate that the analysis of the sedimentological-stratigraphic characteristics of collapse layers allows hypotheses as to the origin of a deposit. In the case of layers formed by building decay or seismic destruction, the stratigraphic analysis defines substantial differences that are indicative of different origins. Indeed, the stratigraphy of collapse deposits due to building decay is made up of fine-to-coarse grained layers, due to the slow accumulation of materials, which are capped by huge fragments of buildings following the final collapse of the structure. For seismic destruction, large fragments of walls or entire pillars and columns, plus the coarse-grained ruins, usually lie over floors and pavements without interposed layers of abandonment. The characterisation of a collapse deposit has implications in archaeoseismological research, i.e. the identification of traces of past earthquakes during archaeological excavations or through the analysis of the archaeological monumental heritage.