The Pinatubo eruption presented the greatest test of immediate prediction and hazard assessment in the past few years, although the safe evacuation of Rabaul at very short notice in September 1994 was also a remarkable achievement. Considering its size and the high population of the surrounding area, the death toll from Pinatubo was small. Most casualties were due to the collapse of buildings under the weight of rain-sodden ash and to mudflows spawned after the main eruption.
Events at Pinatubo, from the first new vents that opened on April 2, to the main eruptions on 12-15 June, escalated quickly but with the combined efforts of the Philippine Volcano Observatory and the U.S. Geological Survey teams, using mainly conventional monitoring techniques and quick decision-making combined with a rapidly obtained record of the volcano's past eruptive record, an effective hazard mitigation plan was developed (Pinatubo Volcano Observatory Team, 1991). Real-time seismic amplitude measurements ( Endo and Murray, 1991) from a small rapidly installed system were particularly useful in tracking magma movements beneath the volcano. Timely evacuation of the endangered population was carried out by Philippine domestic organizations and the U.S. military. There was, of course, tremendous loss of agricultural land and the eruption led to the closing of important military installations such as the U.S. Clarke air base and Subic Bay naval station, with considerable impact to the local economy. Monsoon and typhoon rain-induced mudflows and other catastrophic flows have continued to wreak havoc in areas downslope of Pinatubo since the eruption, greatly extending the zone of devastation around the volcano.