In view that cities will continue to house the majority of the world’s population at an increasing rate in association with the face of climate change, we quantify urban resilience by examining the response history of the mean-square displacement of the citizens of large cities prior and upon historic natural hazards strike. The recorded meansquare displacements of large numbers of cell-phone users from the cities of Houston, Miami and Jacksonville when struck by hurricanes Harvey 2017, Irma 2017 and Dorian 2019, together with the recorded mean-square displacements of the citizens of Dallas, and Houston when experienced the 2021 North American winter storm, revert immediately to their pre-event steady-state response; suggesting that large cities when struck by natural hazards exhibit an inherent resilience. We explain how the mean-square displacement from a random (stochastic) process is intimately related to deterministic time-response functions of emergent mechanical models. We build on this overarching relation that derives from Langevin dynamics and we show that a significant number of records presented in this study validate a mechanical model for cities, recently developed by the authors. Our mechanical model that is inspired from the quantitative theory of Brownian motion predicts that following a natural hazard, large cities revert immediately to their initial steady-state regime and resume their normal, pre-event activities-that is exactly what the recorded data show.
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