Long-term predictions of the time of eruptions using remote distance measurement at Volcلn de Colima, México

Series of up to 37 distance measurements made between remote instrument stations and nine reflectors permanently installed on the dome and summit cone of Volcلn de Colima, México, show accelerating expansion of the summit and upper part of the cone prior to the eruption that began on 20 November 1998. Acceleration began nearly a year before the eruption, and inverse-rate analysis of measured distances indicates that the time of the eruption could have been predicted. The accuracy increases from approximately ±5 weeks for predictions made 25 weeks in advance, down to ±13 to ±15 days for predictions made 4 weeks in advance. More regular measurement at weekly intervals might have greatly improved the accuracy of the predictions. This and other studies suggest that under some circumstances, for example where observed movements are large and intervals between observations short, regularly repeated ground deformation measurements might give satisfactory predictions of the timing of volcanic eruptions earlier than other methods.