火山ハザードマップを用いた全国35 火山における火山噴火ハザード曝露評価

Abstract

我々は全国35 火山のハザードマップを用いて火山噴火ハザード曝露評価を実施した．ハザード種は溶岩流，火砕流，土石流，融雪型泥流，降灰の5 つを扱い，曝露対象は人口，建物，高速道路，国道，在来線線路，新幹線線路とした．ハザードデータはポリゴンであり，GIS ソフトにてハザードポリゴン内に含まれる曝露対象をカウントした．その評価結果に基づき，曝露スコアを算出した．これら評価結果は表にまとめられた．曝露量は富士山噴火によるものが最多であり，降灰，溶岩流，融雪型泥流の影響を大きく受けることが明らかになった．また火砕流への曝露は全国的に相当数確認することができた．降灰，土石流，融雪型泥流は遠方に到達するハザードであるため，火山麓に広がる都市部へ影響があることが評価結果として得られた．

We evaluated exposure to volcanic eruption hazards for 35 volcanoes in Japan using volcanic hazard maps. Five volcanic hazards were considered: lava flow, pyroclastic flow, debris flow, snow-related lahar, and ashfall. The exposure targets were population, buildings, highways, national highways, railways, and bullet train railways. Hazard data were converted to polygons, and GIS software used to count exposure targets included in the hazard polygons. Exposure scores were calculated based on the evaluation result and summarized. This revealed that the amount of exposure to eruption of Fuji volcano was the greatest with large effects of ashfall, lava flow, and snow related lahar. In addition, we confirmed a considerable number of exposures to pyroclastic flows nationwide. The evaluation result also showed impacts on urban areas at the foot of volcanoes due to ashfall, debris flows, and snow-related lahars which extend far away.