市街地避難の性状を支配する不確定要因の影響を考慮した地震火災リスクの評価に関する基礎的検討

摘要

A risk-based evaluation method for countermeasures against seismic-induced fires was developed considering the influences of uncertain factors governing behaviors of urban fire and evacuation. A risk concept was introduced into the proposed method, where the risk was defined as the probability that the ratio of burnt down buildings or burn death people in an administrative unit exceeds a threshold within a given time period from the earthquake. The risk was calculated by a combination of Monte Carlo simulation and physics-based fire/evacuation simulation, where the following uncertain factors were considered to set fire scenarios: (1) ignition; (2) fire fighting at initial stage; (3) weather; (4) structural damage of a building; (5) initial location of an evacuee; and (6) passage obstruction of a road. In this paper, the risk of Kyoto city was evaluated by the assumption of eight kinds of inland earthquakes to validate the availability of the method. As a result, the effect of the measure which enhances fireproof performance of buildings could be quantified with the decrement of the risk.%本研究では，出火や気象，滞留人口といった不確定要因に左右される地震火災被害の評価に，「リスク」の概念を導入することで，安全対策の有効性を合理的に評価可能な手法の基礎的な検討を行った．まず，リスクの一般的な数学表現を，（A）モンテカルロ・シミュレーションと，（B）筆者らの開発による火災性状と避難性状の予測モデル，の両者が利用可能な形に拡張し，地震火災リスクを「ある時間以内に，類焼率（または死亡率）がある値を超える確率」として，国勢統計区といった小地域ごとに定義した．