Risk assessment of Tunguska-type airbursts

The Tunguska airburst, which devastated a taiga forest over an area greater than 2,000 km 2 in a remote region of Central Siberia in 1908, is a classic example of extraterrestrial encounter discussed in the asteroid/comet impact hazard and risk assessment literature (e.g. Longo 2007 ; Carusi et al. 2007 ). Although it is generally agreed that the cosmic body caused damage by bursting in the air rather than through direct impact on the Earth’s surface, the Tunguska event is often referred to as an impact event. To the best of our knowledge, no detailed studies have been performed to quantify the risk of a similar-sized event over a populated region. We propose here a straightforward probabilistic risk model for Tunguska-type events over the continental United States and use established risk metrics to determine the property (buildings and contents) and human losses. We find an annual average property loss of ~USD 200,000/year, a rate of ~0.3 fatalities/year and ~1.0 injuries/year ranging from a factor 3 below and to a factor 3 above the indicated values when a reasonable rate uncertainty for Tunguska-type events is taken into account. We then illustrate the case of an extreme event over the New York metropolitan area. While we estimate that this “nightmare” scenario would lead to ~USD 1.5 trillion of property loss, ~3.9 millions of fatalities and ~4.7 millions of injuries, such event is almost impossible (occurrence once every ~30 million years) and should only be considered as an illustrative example. Copyright Springer Science+Business Media B.V. 2011