4.1 Predicting Damage Levels

The extent and severity of damage and injuries in an explosive event cannot be predicted with perfect certainty. Past events show that the specifics of the failure sequence for an individual building due to airblast effects and debris impact significantly affect the overall level of damage.

For instance, two adjacent columns of a building may be roughly the same distance from the explosion, but only one fails because it is struck by a fragment in a particular way that initiates collapse. The other, by chance, is not struck and remains in place. Similarly, glass failures may occur outside of the predicted areas due to air-blast diffraction effects caused by the arrangement of buildings and their heights in the vicinity of the explosion. The details of the physical setting surrounding a particular occupant may greatly influence the level of injury incurred. The position of the person, seated or standing, facing towards or away from the event as it happens, may result in injuries ranging from minor to severe.

Despite these uncertainties, it is possible to calculate the expected extent of damage and injuries to be expected in an explosive event, based on the size of the explosion, distance from the event, and assumptions about the construction of the building. Additionally, there is strong evidence to support a relationship between injury patterns and structural damage patterns.