This paper aims to investigate the dynamics of fire spreads and their spread ranges following Tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake based on the survey of the affected areas and to clarify the actual firefighting activities of fire brigades and their activity obstacles by interviews with staffs of some Fire Departments. Firefighting activities were organized and classified using KJ method. And based on the result of these analyses, factors of firefighting activity obstacles were specified and structured as difficulties in moving, securing water sources, and spraying of water at devastated area by Tsunami. And it became clear that Tsunami fires spread rapidly while fire fighters evacuated from dangerous area to avoid another Tsunami.
The Great East Japan Earthquake has resulted in the generation of a large amount of rubble, and subsequently, many ‘outdoor rubble storage areas’ have been established in the disaster areas. However, since summer of 2011, about 30 fires occurred in the Tohoku district’s outdoor rubble storage areas. One of the causes of these fires is believed to be the proliferation of microorganisms and fermentation of the organic material present in the rubble piles. The heat generated during fermentation ultimately results in spontaneous ignition. The authors of this study conducted field surveys of two rubble storage areas in Yuriage and Kozukahara, Natori City, Miyagi Prefecture where fires have occurred. Rubble samples containing material conducive to fermentation were collected from the fire-affected areas and the risk of spontaneous ignition triggered by the heat generated during fermentation was examined. The results revealed that the heat generated during fermentation of rotten tatami mats and wood chips is most likely to act as a trigger and become a cause of the fire if adiabatic conditions are good.