Propagation of a volcanic blast (shock wave) induced by the Unzen Volcano on 8 June 1991 explosion has been numerically simulated. The numerical work was done by using the second order finite difference TVD scheme in three dimensional general curvilinear coordinates taking the real topography into account. A constraint for the simulation is the observed value of overpressure of the blast at 2700 m distance from the source crater. The results demonstrate significant effect of local topography on the pressure distributions both on the ground and in the air. For example, the overpressure at the front of Mt. Mayuyama is much higher due to the reflection than that in the case on a smooth ground. The present simulation code is a potential tool for not only the understanding of the propagation of a volcanic blast, but also for making a hazard map if we combine our simulation technique with the knowledge of the distribution of volcanic disaster. In the last section, we made a brief discussion on the future study.
