This study uses numerical modeling to determine the possibility of an edifice collapse at the active Pacaya Volcano in Guatemala. Stability analyses using the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM) were performed on the south-western flank using the physical-mechanical material properties of Pacaya’s intact rocks and rock mass characteristics based on field observations and laboratory tests. The Hoek and Brown failure criterion was used to calculate the friction angle, cohesion, and rock mass parameters in a determined stress range. Volcanic instability was assessed based on the variability of the Factor of Safety and Shear Strength Reduction using deterministic, sensitivity, and probabilistic analyses considering static conditions. Results indicate the volcanic slope is stable under gravity alone, but the possible presence of a layer of pyroclastics significantly reduces the stability of the slope. Future work will focus on verifying the presence of this layer and evaluating the effect of external loading mechanisms such as earthquake load and magma pressure on the slope stability at Pacaya.
Volcanic landslides, which have caused over 20,000 fatalities in the past 400 years [1], are extremely hazardous geologic processes due to their size and velocity. These events can travel at speeds of 50 to 150m/s [2, 3], containing several cubic kilometers of debris and traveling tens of kilometers away from the volcano. Since the sector collapse and associated lateral eruption of Mount St. Helens in 1980, there has been a surge of interest in volcanic collapse mechanisms and collapse evidence. Collapses have now been reported at 400 volcanoes around the world, of which 21 have had a large-volume landslide (>0.1 km³) since 1500 A.D. [4]. Besides the direct impacts on nearby communities due to debris avalanches and associated lahars, they also increase the risk of explosive and/or lateral eruptions.
