The Leaning Tower of Pisa is notable for its pronounced slant, but also because, despite that precarious state, it’s managed to stay standing through four or more significant earthquakes. Researchers have figured out how the structure has pulled that off.


The Leaning Tower of Pisa is notable for its pronounced slant, but also because, despite that precarious state, it's managed to stay standing through four or more significant earthquakes.  An international team of researchers has figured out how the roughly 190-foot-tall, 740-year-old structure has pulled that off.  "After studying available seismological, geotechnical and structural information, the research team concluded that the survival of the Tower can be attributed to a phenomenon known as dynamic soil-structure interaction," according to a release from the University of Bristol. The tower's stature and rigidity combined with the soft soil it's in "causes the vibrational characteristics of the structure to be modified substantially, in such a way that the Tower does not resonate with earthquake ground motion."  "Ironically, the very same soil that caused the leaning instability and brought the Tower to the verge of collapse, can be credited for helping it survive these seismic events," George Mylonakis, one of the researchers, commented.