Unlike mine ventilation seal structures (30 CFR §75.335; Greninger et al. 1991, Mitchell 1971, Weiss et al. 2002) that are commonly used to isolate unused sections of a mine, stoppings are not intended to withstand even moderate explosion overpressures. Unfortunately, mine explosions do occur. Depending on the location and severity, explosions can result in fatalities and injuries to underground mining personnel, and cause considerable damage underground to equipment and structures. MSHA personnel conduct investigations of these explosion accidents to determine the root cause(s) as a means to mitigate or eliminate future occurrences. As part of these post-explosion investigations, the location and condition of underground structures and debris are mapped. This information assists in determining the strength and the direction of the forces of the explosion.