Simulating past and forecasting future eruptive scenarios at San Miguel Volcano, El Salvador

Abstract

San Miguel or Chaparrastique volcano has been active at least for the past 10 ky, erupting 28 times in the last 500 years (historical period). It is consider one of the most active volcanoes of El Salvador. The majority of historical eruptions have been central with ashfall emissions, and only 8 have been effusive flank eruptions mainly giving lava flows. The activity has been mostly Strombolian in nature (VEI 1-2). Products composition is basaltic and basaltic-andesite. The most common volcanic processes associ-ated to the volcano have been ashfall, ballistics, lava flows and secondary lahars. Using the information from these historical eruptions and applying probabilistic tools designed for volcanic hazard assessment, we simulated scenarios related to: (1) the five most likely scenarios obtained from HASSET (ashfall scenarios short-medium extent and VEI 1-2); (2) the most hazardous scenario (ashfall + lava flow + ballistics medium to large extent with VEI 3); and (3) other scenarios related to lava flows and lahars with similar characteristics than those occurred in the historical period. Finally, we constructed a qualitative integrated volcanic hazard map thought the combination of the simulated scenarios. This study has been developed with the aim of improving the already developed emergency plan. It serves as starting point in the collaboration and coordination between scientist, the national observatory (OA-MARN) and the civil protection agency of San Miguel municipality, and poses to strength this cooperation, in a systematic way, to face the future volcanic activity. S02.07