Seismic Reassessment of the Leaning Tower of Pisa: Monitoring, Site Response and SSI

Gabriele Fiorentino, Giuseppe Quaranta, George Mylonakis, Davide Lavorato, Alessandro Pagliaroli, Giorgia Carlucci, Fabio Sabetta, Giuseppe Della Monica, Giuseppe Lanzo, Victoria Aprile, Giuseppe Carlo Marano, Bruno Briseghella, Giorgio Monti, Nunziante Squeglia, Raffaello Bartelletti, Camillo Nuti*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

11 Citations (Scopus)
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The Tower of Pisa survived several strong earthquakes undamaged over the last 650 years, despite its leaning and limited strength and ductility. No credible explanation for its remarkable seismic performance exists to date. A reassessment of this unique case history in light of new seismological, geological, structural, and geotechnical information is reported, aiming to address this question. The following topics are discussed: (1) dynamic structural identification based on recorded earthquake data; (2) geophysical site characterization using a two-dimensional array; (3) seismic hazard and site response analysis considering horizontal and vertical motions; and (4) soil-structure interaction (SSI) analysis calibrated using lab and field data. A substantial shift in natural period, from about 0.35 s to over 1 s (a threefold increase, the largest known for a building of that height) caused by SSI, a wave parameter (1/σ) of about 0.3, and a minor effect of vertical ground motion are identified and may explain the lack of earthquake damage on the Tower. Recommendations for future research, including the need to establish a seismic bedrock deeper than 500 m, are provided.
Original languageEnglish
Pages (from-to)703-736
Number of pages34
JournalEarthquake Spectra
Issue number2
Publication statusPublished - 1 May 2019


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