Tephra2 Probability Tool

The Tephra2 probability tool can probabilistically estimate the mass of tephra that will accumulate at a site over a range of explosive eruption conditions.

Tephra2 Probability Tool - At a Glance

  • Tephra2 is a tephra dispersion model that calculates the expected accumulation of tephra at a point(s), given explosive eruption conditions
  • The code simplifies the eruption conditions, calculating the expected tephra accumulation for a given total eruption mass, eruption column height, and particle size distribution
  • Wind velocity varies as a function of height. Wind velocity is constant within a given stratum
  • Wind velocities as a function of height are sampled from the NOAA REANALYSIS database for the volcano
  • Tephra2-survivor creates a survivor plot, the expected accumulation at a site for a range of eruption and atmospheric conditions
  • Tephra2-survivor will plot a representative isopach map, for a worst case scenario (wind and eruption conditions that maximize accumulation at the site)

Inputs

Tephra2-probability tool input parameters:

  • Volcanic vent location. Choose the volcano from the pull down menu
  • Location of the site. Input the location of the site of interest in Longitutde and Latitude. Use decimal degrees.
  • Elevation (m). Input the elevation of the site in meters above sealevel
  • Choose eruption conditions. Select one or more volcano explosivity index (2-7). This corresponds to a range of eruption masses, column heights, and grain size distributions. You can also specify a fixed eruption mass and column height. In this case only the variation in wind velocity produces variation in the mass of tephra tha accumulates at the site.
  • Choose the number of simulations. More simulations require longer run time, but result in more meaningful results, since more wind fields are sampled and the range of eruption conditions are explored more thoroughly.

Outputs

Tephra2-probability tool outputs:

  • First, a survivor plot is created. One curve is plotted for each set of eruption conditions. For example, separate curves are ploted for each VEI, each representing a range of eruption and wind conditions.
  • You can choose to save the png image of the graph by right clicking on the graph
  • You can download various files used to create the graph, and numerical results
  • Once the graph is created, you can create an isopach map which shows a map view of the worst case scenario (greatest tephra accumulation at the site).

Run Tephra2 Probability Tool ยป

References

  • Bonadonna, C., Connor, C. B., Houghton, B. F., Connor, L., Byrne, M., Laing, A., and Hincks, T. K. (2005) Probabilistic modeling of tephra dispersal: Hazard assessment of a multiphase rhyolitic eruption at Tarawera, New Zealand, Journal of Geophysical Research: Solid Earth 110(B3). DOI 10.1029/2003JB002896
  • Biass, Sebastien, Bagheri, Gholamhossein, Aeberhard, William H., and Bonadonna, Costanza (2014) TError: towards a better quantification of the uncertainty propagated during the characterization of tephra deposits, Statistics in Volcanology 1(2):1-27. DOI 10.5038/2163-338X.1.2
  • Biass, S., Bonadonna, C., Connor, L., and Connor, C. (2016) TephraProb: a Matlab package for probabilistic hazard assessments of tephra fallout, Journal of Applied Volcanology 5(1):10. DOI 10.1186/s13617-016-0050-5