A rule of thumb for firefighters and the “collapse zone” for falling walls is 1.5 times the height of the wall.

That is, if a wall is 30 feet high, when it collapses from loss of structural integrity, such as through a fire, it will cover a distance of approximately 45 feet from the base of the wall, for the length of the wall that collapses.

An explosion would extend the collapse zone, depending on the strength of the explosion.

This should make it quick and easy to deal with this type of scenario, such as a siege or earthquake.

Way back when, I was a volunteer firefighter. My recollection of this rule was wrong, so I’m glad that I googled for the right terminology.