@article{fdi:010062515,
  title = {{P}yroclastic flow erosion and bulking processes : comparing field-based vs. modeling results at {T}ungurahua volcano, {E}cuador},
  author = {{B}ernard, {J}. and {K}elfoun, {K}. and {L}e {P}ennec, {J}ean-{L}uc and {V}argas, {S}. {V}.},
  editor = {},
  language = {{ENG}},
  abstract = {{P}yroclastic density currents ({PDC}s) are high-temperature and high-velocity mixtures that threaten populations in the vicinity of many active volcanoes. {D}eciphering the cause of their remarkable mobility is essential for volcanic hazard analysis, but remains difficult because of the complex processes occurring within the flows. {H}ere, we investigate the effect of bulking on dense {PDC} mobility by means of a double approach. {F}irst, we estimate the amount of material incorporated into scoria flows emplaced during the {A}ugust 2006 eruption of {T}ungurahua volcano, {E}cuador. {F}or this, we carry out a detailed analysis of 3{D}-corrected digital images of well-exposed scoria flow deposits. {C}omponentry analysis indicates that {PDC} bulking occurs principally on the steep (>25 degrees) upper slope of the volcano, and the deposits typically comprise 40-50 wt% of non-juvenile (i.e., accessory and accidental) material. {S}econdly, we develop a simple stress-related grain-by-grain equation of erosion combined with two simple depth-averaged geophysical mass-flow models that compare the bulking mechanism to a non-fluidized and a fluidized flow. {T}wo behaviors based on {C}oulomb and plastic rheologies are used to reproduce, on a first order basis, the 2006 {T}ungurahua {PDC}s. {C}ross-check comparisons between these modeled cases and the erosion pattern inferred from field-based data allow us to evaluate the accuracy of our modeling assumptions. {R}egardless of the rheological regime, the {PDC}-induced erosion pattern of the 2006 {T}ungurahua eruption can only be reproduced by fluctuations of the flow's basal shear stress during emplacement. {S}uch variations are controlled by flow thinning-thickening processes, notably through the formation of a thick non-erosive flow body that pushes a thin frictional erosive front during {PDC} emplacement. {T}he input volume of juvenile material, as well as the thickness of the erodible layer available prior to the eruption, are additional key parameters. {O}ur work highlights complexities in {PDC} erosion and bulking processes that deserve further study. {I}n terms of hazard assessment, our findings reveal that incorporation and bulking translate into increased flow mobility, i.e., the augmented flow mass enhances both flow velocity and runout distance (up to 20 %). {T}hese outcomes should be considered closely for hazard analysis at many other andesitic volcanoes worldwide where similar {PDC} events are common.},
  keywords = {{P}yroclastic density currents ; {E}rosion ; {C}omponentry ; {N}umerical simulation ; {T}ungurahua ; {EQUATEUR}},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {76},
  numero = {9},
  pages = {art. 858 [16 ]},
  ISSN = {0258-8900},
  year = {2014},
  DOI = {10.1007/s00445-014-0858-y},
  URL = {https://www.documentation.ird.fr/hor/fdi:010062515},
}