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.

It is of fundamental importance in engineering design practice to accurately evaluate the structural response of buried pipelines subjected to seismic hazards, like landslides, lateral spreading due to liquefaction, and faulting, because these seriously threaten pipeline safety. The present paper investigates the seismic performance of a buried operating steel pipeline subjected to strike-slip faulting using the continuum finite element modeling approach and considering appropriate equivalent boundaries representing the interaction with the rest of the soil–pipeline system. The latter are derived analytically in terms of an axial spring expressed in function of the soil–pipeline nonlinearities, service loads like the internal pressure and temperature variation, pipeline unanchored length, cross-section area, and the different loading paths either in tension or compression. The obtained analytical and numerical results give a better insight into the mechanical behavior of the soil–pipeline system subjected to strike-slip faulting that induces overall tension in the pipeline under different levels of operating loads. The methodology described in this paper, including the formulation of the equivalent boundaries, can be applied to accurately and efficiently assess the seismic performance of operating buried pipelines subjected to strike-slip fault movement and similar permanent ground deformations (PGDs).