1986年伊豆大島溶岩流のシミュレーションの再検討-噴火中の地形変化の影響について-

Abstract

The fissure eruption occurred at Izu-Oshima on November 21, 1986. The lavas extruded inthe caldera (LB I and LB III) and on the western flank (LC I). These lava flows were simu-lated by the numerical calculation using the topographic map before the eruption. The calculatedlava flow LC I and LB III almost coincided with the actual one, but the lava flow LB I did not.It is inferred that the accumulation of scoria near the vents might divert the lava flow LB I.Considering the topographic change due to the accumulation of scoria, numerical simulation wasmade again and evaluated the effect of the scoria cones. The discrepancy between the calculatedand actual lava flow became small. It was verified that scoria cones diverted the lava flow LB I.A risk map for lava flows at Izu-Oshima is shown. The map expresses the distribution ofassumed craters from which lavas are likely to pass through residential areas.