Simulation of block‐and‐ash flows and ash‐cloud surges of the 2010 eruption of Merapi volcano with a two‐layer model

Kelfoun, Karim; Gueugneau, Valentin; Komorowski, Jean‐Christophe; Aisyah, Nurnaning; Cholik, Noer; Merciecca, Charley

doi:10.1002/2017jb013981

Cited by 37 publications

(42 citation statements)

References 45 publications

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“…The volcano erupted several times during the last few decades, once every 3-5 years on average, with the largest explosive event recorded in 2010. The 2010 eruption removed parts of the summit area (Surono et al, 2012), excavated a ∼ 200 m deep crater and was followed by re-growth of a new dome (Kubanek et al, 2015). The new lava dome was intermittently destroyed by several explosive events again between 2012 and 2014, which also caused elongated open fissures (Fig.…”

Section: Merapi Volcanomentioning

confidence: 99%

“…The pyroclastic surges that occurred and jumped over Kendil hills during the 2010 eruption could not be modeled by Titan2D as surges are diluted, mixed with gas and the propagation is not controlled by topography (Charbonnier et al, 2013). In order to solve the propagation of pyroclastic surge, a two-layer model has been proposed by assuming that pyroclastic density currents (PDCs) consist of two distinct layers, a concentrated layer (block-and-ash flow) and a diluted layer (ash-cloud surge; Kelfoun et al, 2017). The mobility of each layer is solved by using a depth-averaged algorithm.…”

Section: Limitationsmentioning

confidence: 99%

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Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption

Darmawan

Walter

Troll

et al. 2018

Nat. Hazards Earth Syst. Sci.

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Abstract. Lava domes are subjected to structural weakening that can lead to gravitational collapse and produce pyroclastic flows that may travel up to several kilometers from a volcano's summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently causing high numbers of casualties. After the Volcanic Explosivity Index 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a delineated block in the southern dome sector. Here, we investigated the geomorphology, structures, thermal fingerprint, alteration mapping and hazard potential of the Merapi lava dome by using drone-based geomorphologic data and forward-looking thermal infrared images. The block on the southern dome of Merapi is delineated by a horseshoe-shaped structure with a maximum depth of 8 m and it is located on the unbuttressed southern steep flank. We identify intense thermal, fumarole and hydrothermal alteration activities along this horseshoe-shaped structure. We conjecture that hydrothermal alteration may weaken the horseshoe-shaped structure, which then may develop into a failure plane that can lead to gravitational collapse. To test this instability hypothesis, we calculated the factor of safety and ran a numerical model of block-and-ash flow using Titan2D. Results of the factor of safety analysis confirm that intense rainfall events may reduce the internal friction and thus gradually destabilize the dome. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector may travel southward for up to 4 km. This study highlights the relevance of gradual structural weakening of lava domes, which can influence the development fumaroles and hydrothermal alteration activities of cooling lava domes for years after initial emplacement.

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Section: Merapi Volcanomentioning

confidence: 99%

Section: Limitationsmentioning

confidence: 99%

Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption

Darmawan

Walter

Troll

et al. 2018

Nat. Hazards Earth Syst. Sci.

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“…The model must now be tested against real field cases in order to check its ability to quantitatively reproduce natural phenomenon. In a companion paper [ Kelfoun et al ., ], we show that the model is able to reproduce the extension, the thickness, and the emplacement of the 2010 PDCs of Merapi volcano.…”

Section: Resultsmentioning

confidence: 86%

“…The parameters of the following simulations are listed in Table . If not specified, the parameters used are realistic values either obtained by field measurements or estimated by reproducing natural events in the companion paper [ Kelfoun et al ., ].…”

Section: Resultsmentioning

confidence: 99%

A two‐layer depth‐averaged model for both the dilute and the concentrated parts of pyroclastic currents

Kelfoun

2017

JGR Solid Earth

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Pyroclastic currents are very destructive and their complex behavior makes the related hazards difficult to predict. A new numerical model has been developed to simulate the emplacement of both the concentrated and the dilute parts of pyroclastic currents using two coupled depth‐averaged approaches. Interaction laws allow the concentrated current (pyroclastic flow) to generate a dilute current (pyroclastic surge) and, inversely, the dilute current to form a concentrated current or a deposit. The density of the concentrated current is assumed to be constant during emplacement, whereas the density of the dilute current changes depending on the particle supply from the concentrated current and the mass lost through sedimentation. The model is explored theoretically using simplified geometries as proxies for natural source conditions and topographies. It reproduces the relationships observed in the field between the surge genesis and the topography: the increase in surge production in constricted valleys, the decoupling between the concentrated and the dilute currents, and the formation of surge‐derived concentrated flows. The strong nonlinear link between the surge genesis and the velocity of the concentrated flow beneath it could explain the sudden occurrence of powerful and destructive surges and the difficulty of predicting this occurrence. A companion paper compares the results of the model with the field data for the eruption of Merapi in 2010 and demonstrates that the approach is able to reproduce the natural emplacement of the concentrated and the dilute pyroclastic currents studied with good accuracy.

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“…The rock avalanche motion is modelled using the geophysical mass flow code VolcFlow (Kelfoun and Druitt, 2005). VolcFlow has been tested on a number of debris avalanches and pyroclastic flow events, successfully simulating avalanche run-out and emplacement dynamics in a number of settings (Kelfoun and Druitt, 2005;Kelfoun et al, 2008Kelfoun et al, , 2009Kelfoun et al, , 2010Kelfoun et al, , 2017Giachetti et al, 2011;Kelfoun, 2011Kelfoun, , 2017Paris et al, 2011;Charbonnier and Gertisser, 2012;Dondin et al, 2012;Giachetti et al, 2012Giachetti et al, , 2013Manzella et al, 2016). As with many other continuum dynamic models used for simulating rock avalanche propagation (Savage and Hutter, 1989;Iverson et al, 1997;McDougall and Hungr, 2004), VolcFlow is governed by a continuity and momentum equation based on the Saint-Venant equations of shallow flow.…”

Section: Numerical Flow Codementioning

confidence: 99%

Transferability of a calibrated numerical model of rock avalanche run‐out: Application to 20 rock avalanches on the Nuussuaq Peninsula, West Greenland

Benjamin

Rosser

Dunning

et al. 2018

Earth Surf Processes Landf

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Long run‐out rock avalanches are one of the most hazardous geomorphic processes, and risk assessments of the threat they pose are often reliant on numerical modelling of their potential run‐out distance. The development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events. Despite this, few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised, and hence transferrable, rules. We conduct field and imagery‐based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the Nuussuaq peninsula, West Greenland. The rock avalanches run out towards the Vaigat Strait, and are sourced from a range of coastal mountains of relatively uniform geology. We calibrate a three‐dimensional continuum dynamic flow code, VolcFlow, with data from a modern, well‐constrained event that occurred at Paatuut (ad 2000). The best‐fit model assumes a constant retarding stress with a collisional stress coefficient, simulating run‐out to within ±0.3% of that observed. This calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography. Our findings illustrate that a single calibration of VolcFlow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits, emplaced by a series of events spanning a large volume range. Although the prevailing approach of tuning models to a specific case may be useful for detailed back‐analysis of that event, we show that more generally applied models, even using a single pair of rheological parameters, can be used to model potential rock avalanches of varied volumes in a region and, therefore, to assess the risks that they pose. © 2018 John Wiley & Sons, Ltd.

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Simulation of block‐and‐ash flows and ash‐cloud surges of the 2010 eruption of Merapi volcano with a two‐layer model

Cited by 37 publications

References 45 publications

Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption

Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption

A two‐layer depth‐averaged model for both the dilute and the concentrated parts of pyroclastic currents

Transferability of a calibrated numerical model of rock avalanche run‐out: Application to 20 rock avalanches on the Nuussuaq Peninsula, West Greenland

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