Energy coneモデルによるピナツボ火山1991年火砕流の解析 : Frothing型噴火の可能性とマルチフローユニット型火砕流のMobility

概要

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One of the greatest eruptions in this century occurred at Pinatubo volcano in Luzon island, Philippine, in June 1991. Large volume of pyroclastic flow and air fall deposits were ejected in the surrounding areas. In the energy-cone model,the real distribution area of the pyroclastic flow deposits determined from satellite image (MOS MESSR), fits with the cone of 500 m height gas thrust and 7.5° slope angle (φ). This low gas thrust height implies a frothing-type eruption. In the log (tan φ) -log (volume) diagram, pyroclastic flows of simple-flow unit fall on a narrow array with negative slope (simple-flow array). Based on this relationship, the mobility (∝1/tan φ) of the 1991 Pinatubo pyroclastic flows was low in spite of their huge volume and the high aspect ratio. This unbalance can be explained by the fact that the 1991 pyroclastic flows consisted of multiple flow units, since the mobility controlled by the volume of each flow unit.
1993-10-31