Seismic and non‐invasive geophysical surveys for the renovation project of Branciforte Palace in Palermo

Abstract

The renovation project of the historic Branciforte Palace (16th–17th century) in Palermo (Italy) was owned by the Banco di Sicilia Foundation, with the aim for it to become a multi-purpose centre for the promotion of exhibitions and cultural events. In the context of the restoration work, a multi-methodological and non-invasive geophysical study has been carried out. The seismic characterization of the foundation soils was obtained by means of joint interpretations of a vertical seismic profile (VSP), multichannel analysis of surface waves (MASW) and horizontal to vertical spectral ratio (HVSR) microtremor analysis. The mutually constrained inversion of seismic surveys carried out with different techniques made it possible to obtain a robust interpretation of the foundation soils. Moreover, indoor geophysical surveys have been carried out to identify critical issues in the state of conservation of the floors and wall structures. In particular ground penetrating radar (GPR) profiles and an electrical resistivity tomography (ERT) have been carried out on the floor of the stable of the Palace, to evaluate in detail the state of consolidation of the foundation soil, in correspondence of a double row of marble columns, some of which were affected by differential subsidence. The joint interpretation allowed to generate a threedimensional (3D) model of the foundation's subsoil, highlighting the irregular surface of the foundation rock and to identify the main structural voids responsible for subsidence. Furthermore, some supporting columns have been investigated by means of ultrasonic tomography (UST) to verify their state of degradation. Finally, infrared thermography (IRT) images of the internal and external walls and of the vaults highlighted differences in the type of masonry and in the state of the plaster.