Blast radius
A blast radius is the distance from the source that will be affected when an explosion occurs. A blast radius is often associated with bombs, mines, explosive projectiles, and other weapons with an explosive charge.
For instance, a 2000 pound Mk-84 bomb has a blast radius of 400 yards.
Of late, the term is being used for impact analysis in technology parlance. For example, when a particular IT service fails, the users, customers, other dependent services that are affected, fall into Blast Radius.