Casualties by the 3 June 1991 pyroclastic flow at Unzen volcano

The 1990-1995 eruption of Unzen volcano, Japan, was characterized by lava dome growth and pyroclastic flows triggered by dome collapse. One of the largest pyroclastic flows occurred at 4:08 p.m. on June 3, 1991. The associated pyroclastic surge killed 43 people and injured 9 persons. The event was the worst volcanic disaster within a few decades in Japan. The victims due to the pyroclastic surge included following persons: fire brigade members watching for lahars and for safety of houses in the evacuation area, local residents returning home for retrieving their property and goods, press people taking photos of the pyroclastic flow, taxi drivers hired by the press, volcanologists recording volcanic activity on video tape, and policemen [OR a policeman] calling for peoples evacuation. Only a few people who were located near the distal end of the pyroclastic surge could survive. The mortality rate was 100% at the upstream area about 4.3 km from the source. The mortality extended to 69% at the downstream area near the distal end of pyroclastic surge. The overall survival rate (18%) is very low. This fact indicates that the only way to avoid disasters due to pyroclastic flows is to evacuate before they occur. Governments must designate the warned area and/or declare an evacuation instruction for residents to keep people out unconditionally, in cooperation with the volcanologists