TITAN2D simulations of the Chaos Jumbles rockfall avalanche, Lassen Volcanic National Park, California
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Volcanic avalanches represent one of the most hazardous phenomena related to volcanoes, thus their study and their comprehension are necessary for reliable hazard assessments. The Chaos Jumbles avalanche deposit represents an opportunity to investigate one such event. This is the first work in which the Chaos Jumbles avalanche is investigated with computational modeling. The use of TITAN2D to simulate these phenomena is both an opportunity to test this simulation tool, different modified versions of the same DEM, and to determine the values of the main physical parameter that influenced the deposit emplacement. The scooping process applied to the original DEM was a useful tool to obtain a digital elevation model more similar to the pre-event surface and the modified DEMs gave better results, in terms of channelization and inundation area, compared to the original one. Values of volume and basal friction angle obtained from the simulations of the Chaos Jumbles events produced lower values than those estimated by Eppler et al. (1987) with different models. Simulations of future event based on parameters estimated by Eppler et al. (1987) confirmed that a potential avalanche from the remaining part of the collapsed dome would cover a smaller area compared to the three previous avalanches; nevertheless the inundation area resulting from simulations is larger than those outlined by Eppler et. al (1987). Considering the great uncertainties in the physical parameters that controlled the emplacement of these avalanches and the differences between the unknown pre-event topography and the current digital elevation model, TITAN2D resulted in being a very reliable computational tool for simulation of these type of avalanches, giving values of Figure of Merit in Space of up to 75%.