Experience in the short-term eruption forecasting at Volcلn de Colima, México, and public response to forecasts

The persistent eruptive activity of Volcلn de Colima during the last 10 years, and the availability of continuous seismic data from a monitoring system have permitted, in some cases, short-term recognition of eruption precursors on the time scale of days before eruptions. The sought precursory pattern is an accelerated rate of seismic energy release. Several cases of seismicity preceding eruptions are analyzed, and three types of situations are briefly discussed: (a) no precursory patterns can be recognized, (b) precursory patterns are difficult to recognize or appear over time scales too short to allow response, and (c) clear precursory patterns can be recognized. The case of forecasting the November 20, 1998 eruption of Volcلn de Colima, which influenced the public response, is briefly discussed.