Preliminary Evaluation of Volcanic Flank Stability Using Finite Difference Modeling: Citlaltepetl Volcano, Mexico

摘要

Catastrophic volcanic collapses (avalanches) behave mechanically as large-scale landslides. We present a geomechanical study evaluating potential failures of volcanic edifices, by creating two-dimensional numerical models for Citlaltepetl volcano, Mexico. The numerical models were constrained by using the distribution and strength of the involved materials, and the inferred preferential dyke strikes, Through finite element analysis we model two different geological aspects that, according to geological studies at Citlaltepetl, could trigger the most recent collapse: water percolation from snowmelt and strength reduction by hydrothermal alteration. Geological reconstructions and characteristics of previous constructive volcanic stages were used to assess which of the two input parameters dominates the failure process. We modeled the volcano stability while the changing rock mass strength and the extension of the hydrothermally altered zone, in presence and absence of a pore water pressure distribution. We examined the resulting strain conditions and concluded that, at Citlatepetl, the hydrothermal alteration by itself is the dominant process that defines the unstable zones. The presence of water reduces the general stability for the same dry critical zones.