Flank collapse scenarios at Volcلn de Colima, Mexico: A relative instability analysis

Previous studies on debris avalanche deposits of Volcán de Colima suggest a cyclic process of repetitive flank collapses triggered by major eruptions (VEI > 4). The recurrence interval of major collapse events during the last 10,000 years is calculated here using a stochastic approach, yielding a mean recurrence interval of 2698 yr, with an uncertainty range of 180 yr. The analysis yields an increased probability of flank collapse in the interval between − 110 yr and + 345 yr from the present. This generates a series of scenarios ranging from optimistic, considering a collapse within the next 345 years, to pessimistic, derived from the 110 year delay. The analysis of relative mass/volume deficit in the volcano structure, made using the new VOLCANOFIT 2.0 software, and a limit equilibrium analysis on the volcano flanks point to the SW quadrant as potentially the most unstable sector of the edifice under a wide range of scenarios. The TITAN2D numerical model is also used to simulate the extent of debris avalanches caused by failure of the SW flank. This approach may be applied to any volcano with a potential for flank collapse.