The frequency of window damage caused by bolide airbursts: a quarter century case study

We have empirically estimated how often fireball shocks produce overpressure at the ground sufficient to damage windows. Our study used a numerical entry model to estimate the energy deposition and shock production for a suite of 23 energetic fireballs reported by US Government sensors over the last quarter century. For each of these events we estimated the peak overpressure on the ground and the ground area above overpressure thresholds of 200 and 500 Pa where light and heavy window damage, respectively, is expected. Our results suggest that at the highest overpressure it is the rare, large fireballs (such as the Chelyabinsk fireball) which dominate the long-term areal ground footprints for heavy window damage. The height at the fireball peak brightness and the fireball entry angle contribute to the variance in ground overpressure, with lower heights and shallower angles producing larger ground footprints and more potential damage. The effective threshold energy for fireballs to produce heavy window damage is ~5 - 10 kT; such fireballs occur globally once every one to two years. These largest annual bolide events, should they occur over a major urban centre with large numbers of windows, can be expected to produce economically significant window damage. However, the mean frequency of heavy window damage (overpressure above 500 Pa) from fireball shock waves occurring over urban areas is estimated to be approximately once every 5000 years. Light window damage (overpressure above 200 Pa) is expected every ~600 years.