The foreground upright structure is the first Torii gate entrance to the Gokoku Shrine. Note the concrete lantern at the foremost ground, around the left side of the middle spot angling downward. That spot received the rays of the blast and became white. The right side of the spot is unaffected because of the shading by the spreading lantern top. Indication is that the blast came from the upper left side of the pictured area, 200 meters from center of explosion.