Hiroshima Gas Co., Inc. (Upper Left)
With the A-bomb explosion, an extremely high pressure of several hundred thousand millibars was generated at the burst point and the surrounding air expanded quickly. creating a tremendous blast. The edge of the blast advanced as a supersonic shock wave followed by the blast itself. The shock wave traveling directly from the center of the explosion and the shock waves reflected from the ground and buildings affected each other, creating a variety of significant damage on the ground. After about ten seconds, the shock wave had traveled approximately 3.7 km from the hypocenter.
At the hypocenter, the maximum pressure of the blast was 35 tons per square meter and the maximum wind speed was 440 meters per second. Three kilometers from the hypocenter, the pressure and wind speed reached l.3 tons per square meter and 30 meters per second, respectively. The force of the blast decreased with distance from the hypocenter, but it was still strong enough to knock over the stone railing of Miyuki Bridge, approximately 2.3 km away.
As the unimaginable blast subsided after blowing from the hypocenter toward the outlying areas, a vacuum of air and pressure was generated in the center. The wind reversed direction and began blowing towards the center from the outlying areas with the intensity of another blast.
Buildings sustained major damage due to the intense shock wave and blast. Wooden structures within 2.3 km of the hypocenter were almost all destroyed and sustained irreparable damage up to 2.6 km from the hypocenter. Up to 3.2 km from the hypocenter, doors, wood-and-paper sliding doors and other fittings were blown away and roof tiles were knocked loose.
Damage on household fittings was seen at a distance of up to 6 km, roof-tiles sliding down at up to 8 km and breaking or cracking of glass at up to 27 km.
Concrete buildings around the hypocenter were severely damaged. The roofs crashed down. Windows and doors as well as their frames were totally blown away. All other fittings were smashed, scattered and burned in the fires that immediately followed the bombing. Concrete buildings within 1 km of the hypocenter endured the blast but their interiors were destroyed by fires. In buildings up to 2 km from the hypocenter, windows which faced the hypocenter were completely blown away together with their frames.
Hiroshima Gas Co., Inc. (Upper Left)
