Sonic tomography and flat-jack tests as complementary investigation procedures for the stone pillars of the temple of S. Nicolò l'Arena (Italy)

After an earthquake, which struck the Eastern part of Sicily in 1990, some structural elements of the Church of S. Nicolo l'Arena in Catania, as the dome and the vaults, were damaged; vertical cracks on the two pillars were detected. It is not clear whether those cracks were already visible and were simply propagating during the earthquake. It is known that the two pillars probably belong to the original construction of the church. An investigation programme (including historical research and experimental investigation with sonic, radar, flat-jack, coring, boroscopy, etc.) has been recently planned to design the preservation and restoration actions. The results obtained from sonic tests were compared to the results of the other type of tests in order to set up an investigation procedure useful for these cases. The paper presents and discusses the preliminary results of the research carried out by the authors.