Evacuation of a large number of residents is conceivable in case of urban fires following a large earthquake. It is essential to implement an effective evacuation plan for ensuring residents' safety. We have been developing a simulation model based on the potential theory for the evacuation behaviors of city residents, which has been validated by comparing the predicted and the recorded evacuation behaviors of residents in the Great Kanto Earthquake Fire. In this model, fire spread was estimated based on after event field survey of the fire. However, in case of an evacuation simulation in a post-earthquake fire which may take place in future, it is essential to predict the fire spread itself. In this study, a computationally efficient model for post-earthquake fire spread in a large-scale urban area was developed based on several findings established in the field of fire safety engineering. In the proposed model, fire behaviors inside a building were formulated into quasi-steady state equations in order to reduce computational load, and the data quantity in calculation was minimized for applying to fire spread in a large-scale urban area. In this paper, the fire spread in the Sakata City Fire in 1976 was simulated for the model validation and the results were discussed in terms of fire spread behavior, computational speed and data quantity in calculation. The obtained results showed that the proposed model could simulate the fire spread with reasonable accuracy and with much less computation time and data quantity.
