Numerical analysis of the rheological behaviour of the Socompa debris avalanche, Chile

Socompa Volcano provides one of the world’s best-exposed example of a sector collapse that generated debris avalanche deposit. The debris avalanche, occurred about 7000 years ago, involved 25 km3 of fragmented rock that formed a thin but widespread (500 km2) deposit. Numerical model of this event was already performed using a shock-capturing method based on double upwind Eulerian scheme in order to provide information for investigating, within realistic geological context, its dynamic and run-out (Kelfoun and Druitt 2005). This paper analyses an important aspect of the continuum numerical modeling of rapid landslides as debris avalanche: the interchangeability of rheological parameter values. The main question is: by using the same rheological parameter values, are the results, obtained with codes that implement the same constitutive equations but different numerical solvers, equal? Answering this question has required to compare the previous back analysis results with new numerical analyses performed using RASH3D code. Different rheological laws were selected and calibrated in order to identify the law that better fits the characteristics of the final debris deposit of the Socompa landslide.