Physical Effects Caused by the Nagasaki Atomic Bombing
Equivalent in force to 21 kilotons of gunpowder (TNT), the Nagasaki atomic bomb generated levels of blast and heat that cannot even be compared to those produced by conventional weapons. Radiation was released in addition to the ferocious blast wind and heat rays (radiant heat). It is thought that 50%, 35% and 15% of the total energy output was blast, heat and radiation, respectively.
Analysis of all data in 1976 revealed the estimated height to be 503±10m (Kerr & Solomon). Kerr GD, Solomon DL: The epicenter of the Nagasaki weapon-A reanalysis of available data with recommended values. ORNL-TM-5139 (1976)