Numerical modeling of the emplacement of Socompa rock avalanche, Chile

Abstract

[1] The 7.5 ka Socompa sector collapse emplaced 25 km 3 of fragmented rock as a thin, but widespread (500 km 2 ), avalanche deposit, followed by late stage sliding of 11 km 3 as Toreva blocks. Most of the avalanche mass was emplaced dry, although saturation of a basal shear layer cannot be excluded. Modeling was carried out using the depth-averaged granular flow equations in order to provide information on the flow behavior of this well-preserved, long run-out avalanche. Results were constrained using structures preserved on the surface of the deposit, as well as by deposit outline and run-up (a proxy for velocity). Models assuming constant dynamic friction fail to produce realistic results because the low basal friction angles (1 to 3.5°) necessary to generate observed run-out permit neither adequate deposition on slopes nor preservation of significant morphology on the deposit surface. A reasonable fit is obtained, however, if the avalanche is assumed simply to experience a constant retarding stress of 50-100 kPa during flow. This permits long run-out as well as deposition on slopes and preservation of realistic depositional morphology. In particular the model explains a prominent topographic escarpment on the deposit surface as the frozen front of a huge wave of debris reflected off surrounding hills. The result that Socompa avalanche experienced a small, approximately constant retarding stress during emplacement is consistent with a previously published analysis of avalanche data.Citation: Kelfoun, K., and T. H. Druitt (2005), Numerical modeling of the emplacement of Socompa rock avalanche, Chile,

Chapter 10 The effect of topography on ash-cloud surge generation and propagation

“…A variety of geophysical flow models exist for simulating the dense concentrated parts of pyroclastic density currents (PDCs) (Sheridan et al 2004;Kelfoun & Druitt 2005;Patra et al 2005;Kelfoun et al 2009) or for simulating the dilute ash-cloud surges (Ishimine 2005). However, because these models use simplified rheological laws that capture the bulk flow behaviour, they cannot model the dense basal avalanches and ash-cloud surges as a coupled dense -dilute system.…”

Simulation of Pyroclastic Density Current by Lava Dome Collapse at Jeju Island Using TITAN2D

“…Soc. Korea 화성쇄설밀도류에 대한 재난을 모의하기 위하여 TITAN2D (Sheridan et al, 2005), VolcFlow (Kelfoun and Druitt, 2005;Kelfoun et al, 2008;)나 Flow3D (Sheridan et al, 2000) 등과 같은 수치모의 프로그램들이 개발되어 왔으며, 이들 중 국내에서는 백두산에서 발생 가능한 화쇄류의 모의를 위하여 TITAN2D (Yun et al, 2013;와 VolcFlow (Chang and Yun, 2015)가 사용되었다. 본 연구에서는 백두산 의 화쇄류 수치모의를 위해 Yun et al(2013Yun et al( , 2014 (Lee and Yun, 2012 (Kim and Lee, 2000;Sohn and Park, 2004;Sohn et al, 2008;Sohn and Yoon, 2010;Brenna et al, 2012aBrenna et al, , 2012b.…”

Remote sensing study of sector collapses and debris avalanche deposits at Oldoinyo Lengai and Kerimasi volcanoes, Tanzania

“…Basic energy conservation (rgH5Krv 2 ) at a large-volume DAD such as Socompa (H,3000 m), assuming no friction loss, would suggest a maximum velocity of 245 m s 21 whereas numerical modelling suggested maximum speeds of ,100 m s 21 (e.g. Kelfoun and Druitt 2005). At a small-volume DA such as the Boxing Day sector collapse in Montserrat (H,1000 m), energy conservation with no friction loss suggests maximum velocities of 135 m s 21 whereas maximum velocities of 40 m s 21 were derived by observations and numerical modelling (Voight et al 2002).…”

“…They produce debris avalanche deposits (DADs) that can be considerably larger (,1 to 50 km 3 for on-land volcano collapses) and more mobile than non-volcanic landslides (Ui et al 2000, Siebert 2002, for reasons that remain unclear and controversial (e.g. Kelfoun and Druitt 2005). Debris avalanches (DAs) can travel, at initial velocities of up to ,100 m/s, several tens of kilometres beyond the volcano base and can cover an extensive area (from ,10 to .1000 km 2 ).…”