Study on the evaluation of explosion energy of volcanic eruption and on the blast disaster.

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The purpose of present study is to develope the methods for the evaluation of explosion energy of volcanic eruption, and to relate the energy to the geological and disaster distribution owing to the volcanic explosion.The distributions of the disaster and pyroclastic sediment due to the explosion is generally belived to be related directly to the explosion energy. If this assumption is valid, and if we know the energy, we can predict the distributions of those phenomena using a numerical simulation. To prove this assumption, we made following two attempts ; the development of methods for the evaluation of the explosion energy, the explanataion of relation between the explosion energy and the distributions of disaster and pyroclastic sediment. We could get following results ;(1) The maximum distance of pyroclastic surge due to the volcanic explosion is determined only by the explosion energy.(2) The diameter of volcanic crater is in proportion to the explosion energy to the two over three power. The relation for the artificial results (chemical and nuclear explosions) also holds for the case of volcanic explosion.(3) The energy conversion rates from thermal energy to the explosion energy are 0.01-0.4% for magmatic explosion, and 0.4-7% for phreatomagmatic explosion.(4) The rates mentioned above means that we can evaluate the maximum distance of distributions of geological and disaster phenomena if we know the information on the total heat using geomagnetic method or any other methods.(5) The maximum explosion energy we measured in 1994-1995 at Aso Volcano was about 5*10^<15> erg.