Spatio-temporal hazard estimation in San Miguel volcano, El Salvador

Abstract

Despite being one of the most active volcanoes in El Salvador, San Miguel is surrounded by important population nuclei and infrastructures. We used existing historical records of past eruptive activity, available geological knowledge and monitoring data gathered over the past sixteen years to conduct the first comprehensive, long-term hazard assessment of this volcano, aimed at helping to reduce the potential risk it poses. We applied probabilistic methods (QVAST and HASSET) specifically designed for volcanic hazard assessment to conduct two hazard analyses, one with a forecasting time window of two years using information on volcanic activity over the past 430years (historical period), and another with a forecasting window of six months, with information from the past 16years (monitoring period). In both cases we used the same susceptibility map constructed using the most relevant structural elements, which indicates the spatial probabilities of hosting a new vent on San Miguel volcano. Then, we calculated the most likely eruptive scenarios for each analysis and their corresponding forecasting windows, which revealed that the most hazardous areas correspond to Conacastal canton and hamlets of San Jorge, San Miguel and San Rafael Oriente – all lie within 5km of the central crater on the northern and southern flanks. This methodology is easy to update, and results can be improved by incorporating new information. This long-term hazard assessment is a significant contribution that will enable local authorities to implement more rational territorial planning and to design better emergency plans for coping with future volcanic crises.