Sigmoidal particle density distribution in a subplinian scoria fall deposit

Eychenne, Julia; Pennec, Jean–Luc Le

doi:10.1007/s00445-012-0671-4

Cited by 49 publications

(36 citation statements)

References 18 publications

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“…Higher densities are likely for finer grain sizes, especially at size fractions where glass shards, rather than vesicular grains, dominate (cf. Eychenne and Le Pennec 2012).…”

Section: Grain-size Distributionsmentioning

confidence: 99%

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

et al. 2015

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Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single-particle sedimentation from the base of the eruption plume. Here, we document a secondary thickness maximum in a ∼9.75 ka tephra fall deposit from Chaitén volcano, Chile (Cha1 eruption). This secondary thickness maximum is notably coarser-grained than documented historical examples, being dominated by medium-grained ash, and an origin via particle aggregation is therefore unlikely. In the region of secondary thickening, we propose that high levels of atmospheric turbulence accelerated particles held within the mid-to lower-troposphere (0 to ∼6 km) towards the ground surface. We suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves, generated by winds passing over elevated topography beneath the eruption plume. Lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales, particularly in areas of complex topography.

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“…Higher densities are likely for finer grain sizes, especially at size fractions where glass shards, rather than vesicular grains, dominate (cf. Eychenne and Le Pennec 2012).…”

Section: Grain-size Distributionsmentioning

confidence: 99%

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

et al. 2015

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“…Houghton and Wilson, 1989;Eychenne and Le Pennec, 2012) or using simple parameterizations (Bonadonna and Phillips, 2003).…”

Section: Modellingmentioning

confidence: 99%

Tephra hazard assessment at Mt. Etna (Italy)

Scollo

Coltelli

Bonadonna

et al. 2013

Nat. Hazards Earth Syst. Sci.

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Abstract. In this paper we present a probabilistic hazard assessment for tephra fallout at Mt. Etna (Italy) associated with both short-and long-lived eruptions. Eruptive scenarios and eruption source parameters were defined based on the geological record, while an advection-diffusion-sedimentation model was used to capture the variation in wind speed and direction with time after calibration with the field data. Two different types of eruptions were considered in our analysis: eruptions associated with strong short-lived plumes and eruptions associated with weak long-lived plumes. Our probabilistic approach was based on one eruption scenario for both types and on an eruption range scenario for eruptions producing weak long-lived plumes. Due to the prevailing wind direction, the eastern flanks are the most affected by tephra deposition, with the 122 BC Plinian and 2002-2003 eruptions showing the highest impact both on infrastructures and agriculture.

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“…3c, the obtained TGSD is expressed on wt% as a function of the diameter in the φ scale. In red, we plot the assumed particles density according to Eychenne and Le Pennec (2012).…”

Section: Inversion Result: Simulated Scenariomentioning

confidence: 99%

“…Particles are assumed non spherical with a shape-factor of 0.43 within the range presented in Andronico et al (2014b). Density is assumed varying with particles size according to Eychenne and Le Pennec (2012). Exit velocity and radius have been varied hourly.…”

Section: Application To 24 November 2006 Eruption At Mt Etnamentioning

confidence: 99%

Reconstructing eruptive source parameters from tephra deposit: a numerical study of medium-sized explosive eruptions at Etna volcano

2016

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Since the 1970s, multiple reconstruction techniques have been proposed and are currently used, to extrapolate and quantify eruptive parameters from sampled tephra fall deposit datasets. Atmospheric transport and deposition processes strongly control the spatial distribution of tephra deposit; therefore, a large uncertainty affects mass derived estimations especially for fall layer that are not well exposed. This paper has two main aims: the first is to analyse the sensitivity to the deposit sampling strategy of reconstruction techniques. The second is to assess whether there are differences between the modelled values for emitted mass and grainsize, versus values estimated from the deposits. We find significant differences and propose a new correction strategy. A numerical approach is demonstrated by simulating with a dispersal code a mild explosive event occurring at Mt. Now at Icelandic Meteorological Office, Reykjavík, Iceland using available tephra information collected after the eruption. A full synthetic deposit is created by integrating the deposited mass computed by the model over the computational domain (i.e., an area of 7.5 × 10 4 km 2 ). A statistical analysis based on 2000 sampling tests of 50 sampling points shows a large variability, up to 50 % for all the reconstruction techniques. Moreover, for some test examples Power Law errors are larger than estimated uncertainty. A similar analysis, on simulated grain-size classes, shows how spatial sampling limitations strongly reduce the utility of available information on the total grain size distribution. For example, information on particles coarser than φ(−4) is completely lost when sampling at 1.5 km from the vent for all columns with heights less than 2000 m above the vent. To correct for this effect an optimal sampling strategy and a new reconstruction method are presented. A sensitivity study shows that our method can be extended to a wide range of eruptive scenarios including those in which aggregation processes are important. The new correction method allows an estimate of the deficiency for each simulated class in calculated mass deposited, providing reliable estimation of uncertainties in the reconstructed total (whole deposit) grainsize distribution.

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Sigmoidal particle density distribution in a subplinian scoria fall deposit

Cited by 49 publications

References 18 publications

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

Tephra hazard assessment at Mt. Etna (Italy)

Reconstructing eruptive source parameters from tephra deposit: a numerical study of medium-sized explosive eruptions at Etna volcano

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