Archaeology and earthquakes in Siena (Italy). Preliminary results from the survey of the historical buildings in the Terzo di Città

From Firenze University Press Journal: Restauro Archeologico

Andrea Arrighetti, University of Siena

Hélène Dessales, École normale supérieure

In the field of archaeology, in recent decades, increasing value has been placed on the concept of archaeoseismology. This is a term used to indicate the archaeological study of the effects of earthquakes on ancient buildings, being in a state of ruin or preserved (wholly or in part). The concept has seen significant use in the context of archaeological excavations. In contrast, there is a distinct difference when considering the archaeological study of historical buildings. The archaeology of architecture has attempted to develop general procedures in the analysis of individual case studies through a theoretical and methodological approach, thus integrating archaeology while at the same time safeguarding historic buildings from seismic effects. These architectural features constitute specific solutions employed in buildings to resist, mitigate or prevent the effects of earthquakes. Although these techniques were already used in the past, probably as a form of empirical experimentation applied in the formation of widespread aspects of seismic damage, there is still no clear understanding of their actual development and diffusion across specific geographic areas and chronological periods.

During the Middle Ages, elements such as these were frequently found in buildings but rarely referred to in written sources, thus complicating their study. Consequently, architectures themselves became the main source from which we now can understand the spread, as well as the historical and geographical development, of this building phenomenon. This constitutes an element of great interest, characterized by a dual-status: on the one hand, as a form of historical evidence associated with political, economic, and social dynamics that affected the context of study in a given historical period. On the other, as a technical-scientific profile originating from the documentation, characterization, and assessment of these elements because of future restoration or intervention projects compatible with ancient structures. The PROTECT project (www.protect.altervista.org), funded through the Horizon 2020 research and innovation program of the European Union, has been structured with a view to this idea1. The project aims to apply, on an experimental basis, the methods of archaeoseismological analysis to the architectural structures in a portion of the historic center of Siena (Tuscany), to establish new procedures for damage documentation and post-seismic repair techniques of historical buildings. The analysis of this context will focus on edifices from the Late Middle Ages in view of the fact that during this historical period, and specifically in the 15th century, a significant seismic event occurred in Siena, with an estimated intensity of VII. The project is based on a highly interdisciplinary methodological approach, which allows complete analysis and documentation of the identified cases. This is followed by a series of technical, scientific and historical-archaeological results.What is presented here is the first step toward analyzing the context of the study. The first survey results of those features that could be defined as post-seismic conservation elements, in particular, are visible on the external surfaces of historical architectures present in the center of Siena in an area known as Terzo di Città. As illustrated in detail below, the autoptic analysis of the buildings was carried out through an expeditious archaeological reading of the buildings’ street fronts. That was followed by recording elements of interest and their registration in a GIS platform. The possibility of documenting and geolocating these elements, and comparing them with a series of de-tailed cartographic sources, has permitted the first considerations on the use of these techniques in specific areas, according to the characteristics of soil and architecture.

DOI: https://doi.org/10.36253/rar-13099

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