Destructive capability and the mitigation of pyroclastic flows and surges

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1. An extensive field work was made on the disasters done by the pyroclastic flow of June 3,1991. Even after the cessation of the eruptive activity of Fugendake, there is a wide area left off limits to the general public because of possible danger. This made our field investigation difficult and incomplete but an effort was made to carry out field investigation of the main part of the pyroclastic flow, pyroclastic surges and seared zones.2. Interviews were made with civil defense specialists, hospital medical doctors and others, who participated rescue operations during the crises. Comparison was then made with the results of BAXTER (1989).3. Detailed interviews were made with witnesses who encountered the pyroclastic surge of June 3,1991, many of them received burns but survived. Special emphasis was put on the topics of physical damages and the time sequences of the phenomena associated with the on-slaught of the pyroclastic surge. The most valuable testimonies were given by a taxi driver, people who were in their houses when attacked by the surge and later escaped, and those who witnessed the pyroclastic flow from the safe, southern side.4. Based on these testimonies and collected physical evidences, physical and medical effects of surges on buildings, trees, and humans were assessed. Most, if not all of the victims were in the zone of pyroclastic surge where they died of introduction of hot ash into their winds and of heavy skin burns. No severe physical damages were evident when they were struck by the surge in the open. Possible ways of mitigating the damage were discussed, including the possible way of escaping from serious burns and inhaling hot ash.