Seismic Data Interferometry on Structure Monitoring

The dynamic characterization of the historical structures is fundamental in order to estimate their seismic vulnerability and make them more durable. This thesis studies the Angera Bell Tower, a medieval stone tower on the southeastern shore of Lago Maggiore, that is under monitoring through ambient vibration techniques, using ambient vibration interferometry and spectral analyses. Five seismic sensors were deployed at various elevations along the tower, and continuous ambient noise recordings were collected over two separate one-week intervals: the first in late July 2022 and the second in late August 2022, each including a regional earthquake. A comprehensive multi- method analysis was conducted on this dataset, combining waveform inspection, power spectral density (PPSD) analysis, spectrogram evaluation, and cross-component ambient noise interferometry. Additionally, group velocity dispersion curves were computed to investigate frequency-dependent wave propagation, and shear velocity estimations were performed to characterize the tower’s stiffness. The study shows that the combination of ambient noise interferometry with complementary signal processing techniques can be a guideline for understanding the vibrational behavior of complex, heritage masonry towers. This method is an important substitute for when invasive testing is not allowed or applicable. All in all, it helps provide insight for future structural health monitoring applications in historical buildings.