Modeling of partial dome collapse of La Soufrière of Guadeloupe volcano: implications for hazard assessment and monitoring

Abstract

Over the past 9,150 years, at least 9 flank collapses have been identified in the history of La Soufrière of Guadeloupe volcano. On account of the volcano’s current unrest, the possibility of such a flank collapse should not be dismissed in assessing hazards for future eruptive magmatic as well as non-magmatic scenarios. We combine morphological and geophysical data to identify seven unstable structures (volumes ranging from 1 × 106 m3 to 100 × 106 m3), including one that has a volume compatible with the last recorded flank collapse in 1530 CE. We model their dynamics and emplacement with the SHALTOP numerical model and a simple Coulomb friction law. The best-fit friction coefficient to reproduce the 1530 CE event is tan(7°) = 0.13, suggesting the transformation of the debris avalanche into a debris flow, which is confirmed by the texture of mapped deposits. Various friction angles are tested to investigate less water-rich and less mobile avalanches. The most densely populated areas of Saint-Claude and Basse-Terre, and an area of Gourbeyre south of the Palmiste ridge, are primarily exposed in the case of the more voluminous and mobile flank collapse scenarios considered. However, topography has a prominent role in controlling flow dynamics, with barrier effects and multiple channels. Classical mobility indicators, such as the Heim’s ratio, are thus not adequate for a comprehensive hazard analysis.

Topography Curvature Effects in Thin‐Layer Models for Gravity‐Driven Flows Without Bed Erosion

“…In order to investigate the influence of curvature forces in numerical simulations, we use the SHALTOP numerical model (Mangeney et al, 2007). It has been used to reproduce both experimental dry granular flows (Mangeney et al, 2007) and real landslides (Brunet et al, 2017;Favreau et al, 2010;Lucas & Mangeney, 2007;Lucas et al, 2011Lucas et al, , 2014Moretti et al, 2015Moretti et al, , 2020bPeruzzetto et al, 2019). We choose not to compare SHAL-TOP to another code that would not describe precisely the topography effects.…”

Modelling pyroclastic density currents from a subplinian eruption at La Soufrière de Guadeloupe (West Indies, France)

“…This work thus contributes to a volcanic risk assessment strategy in Guadeloupe initiated several years ago (Komorowski et al 2005(Komorowski et al , 2008(Komorowski et al , 2013Hincks et al 2014;Legendre 2012;Peruzzetto et al 2019;Leone et al 2019), with the first integrated hazard map for SDG being produced by Komorowski et al (2005). Subsequently a first attempt to characterize the eruptive behaviour in a systematic way was carried out by Komorowski et al (2008), who defined a logical event tree for magmatic unrest and eruptions.…”

A geophysical index to map alteration, permeability, and mechanical properties within volcanoes. Application to the soft volcanic rocks from Whakaari/White Island (New Zealand)

“…(2) and (3) can be used in conjunction with this method to map the 3D permeability and strength structure of active volcanoes worldwide. These properties, as discussed in the introduction, are important for models of outgassing (e.g., Collinson and Neuberg, 2012;Chevalier et al, 2017), hydrothermal models (e.g., Todesco et al, 2010;Chiodini et al, 2010;Fournier and Chardot, 2012), and flank and dome stability models (e.g., Watters et al, 2000;Finn et al, 2001;Reid et al, 2001;John et al, 2008;Harnett et al, 2018;Peruzzetto et al, 2019).…”

“…The stability of volcanic edifices denotes a significant geohazard (e.g., McGuire, 1996;Voight, 2000) which rests, in part, on the mechanical properties of the edifice-forming rocks. Hydrothermal alteration, common to many active volcanoes worldwide (Zimbelman et al, 2005;Rosas-Carbajal et al, 2016), can modify the physical properties of volcanic rocks (e.g., Pola et al, 2012;Wyering et al, 2014;Frolova et al, 2014;Mordensky et al, 2019), which can lead to an increased risk of edifice instability (e.g., Watters et al, 2000;Finn et al, 2001;Reid et al, 2001;John et al, 2008;Peruzzetto et al, 2019). The permeability of volcanic rocks, a metric considered important in dictating the volcanic character-effusive or explosive-of a volcano (e.g., Eichelberger et al, 1986;Mueller et al, 2008;Collinson and Neuberg, 2012;Farquharson et al, 2017;Cassidy et al, 2018), can also be influenced by hydrothermal alteration (e.g., Sruoga et al, 2004;Heap et al, 2017;Mordensky et al, 2018;Heap et al, , 2020.…”