In the second film of the Gamera trilogy, Gamera encounters an extraterrestrial colony of silicon based organisms called the Symbiotic Legion, led by the Legion Queen. The swarm attacks several cities on Earth, attempting to set up a fertilized flower for reproduction. This is no ordinary flower however, as the swarm expects to use this flower to colonize elsewhere. The seed is therefore launched by a deadly explosion with enough force to reach into space. Gamera, who notably possesses the ability to contain fire, attempts to stop this seed from leaving. The explosion destroys Sendai's Miyagi district.
The river, the dividing traintracks and the crater nearly reaching the large wooded areas are defining areas for the explosion. Set of buildings in area, pinpoint Gamera. The diameter of the destruction is furthermore stated on paper as well as noted to have a 100% rate of building collapse.
Explosion was noted in the newspaper to have produced damage on the level of a major earthquake. (pi*h^2/3)(3*r - h) (pi*533.69^2/3)(3*3000 - 533.69)
2525229853.8 m^3 = 2.5252298538e+15 cm^3
2.5252298538e+15 * 214.35 joules/cc = 5.4128302e+17 joules
It was shown however, that the damage would have 12 kilometer diameter, had gamera not interfered with the explosion.
00:28:18,229 --> 00:28:19,696
how much damage?
00:28:20,699 --> 00:28:24,567
A 6Km radius around downtown
Sapporo would be destroyed for sure.
As a hypothetical, an identical shape with twice the diameter:
.(pi* 1067.38^2/3)(3*6000 - 1067.38)
20201838830.43875 m^3 = 20201838830438752 cm^3
20201838830438752 * 214.35 j/cc = 4.3302642e+18 Joules
At least Mountain level, likely Large Mountain level