Historic buildings like the Basilica of Santa Maria di Collemaggio, a medieval church in L’Aquila, Italy, are vulnerable to earthquakes. An April 6, 2009, earthquake measuring 6.3 MW hit central Italy and damaged the basilica, causing the partial collapse of its dome. An initial investigation analyzed the damage to the structural and architectural elements to facilitate design reconstruction and rehabilitation. In a second study in 2019, researchers performed new sonic tests using the same methodologies and applied the spectral ratio technique, better known as horizontal-to-vertical spectral ratio. HVSR helps to determine the frequency at which the ground motion is amplified during an earthquake. These two studies were analyzed in a new paper in the Journal of Architectural Engineering, “Detection of 2009 L’Aquila’s Earthquake Effects on Collemaggio Church through Experimental Surveys.”
Authors Salvatore Russo, Eleonora Spoldi, Ileana Ippolito, Giacomo Imposa, and Alberto Bretini compared sonic test data collected in 2009 with the data collected in the 2019 survey, following the completion of the structural recovery interventions. Read their research to learn how processing the data using the HVSR technique offered a better understanding of the subsoil features. Their paper is available in the ASCE Library at https://doi.org/10.1061/(ASCE)AE.1943-5568.0000495. Here is its abstract.
Ten years after the earthquake that affected central Italy in 2009, noninvasive investigations were carried out in L’Aquila on the Basilica of Santa Maria di Collemaggio. These were conducted to characterize the ground from a site-response point of view. The study consisted of 11 ambient noise recordings using the Nakamura technique and distributed along two profiles: one longitudinal to the central nave and one transverse. Analyzing the results, it was possible to determine the frequency of the vibration of the ground. After comparison with data from previous literature, it was possible to graph the contrasting sections of the impedance of the subsoil up to about 300 m depth (bedrock) drawing on a passive seismic survey from the single station. Furthermore, sonic tests were performed on the 14 octagonal columns of the central nave. The data were compared with those collected 10 years earlier (post earthquake) and with postearthquake structural restorations. The new tests show an increase of velocity in the resistant sections of the pillars subjected to the structural consolidation.
Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)AE.1943-5568.0000495