By Costanza Bonadonna1, Laura J Connor2, Chuck B Connor2, Leah Michelle Courtland2

1. University of Geneva, Switzerland 2. University of South Florida (USF)

Tephra2 uses the advection diffusion equation to forecast tephra dispersion in a given location based on a user-defined set of eruptive conditions.

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Numerical models used for tephra hazard assessment (Hazard Models) typically result from the combination and integration of different theories and modeling approaches depending on the specific eruptive scenario and mitigation program required. They can be grouped within two main categories: particle-tracking models and advection-diffusion models. Particle-tracking models are Eulerian or Lagrangian models that can forecast volcanic-cloud position at specific times and space. They are mainly used for aviation-safety purposes. Advection-diffusion models are Eulerian models that describe the solution of the equations of particle diffusion, transport, and sedimentation and can forecast tephra accumulation on the ground relative to a particle-release source. These models are mainly used for civil protection purposes, such as giving public warnings and planning mitigation measures. TEPHRA2 is written in C and is used to forecast tephra accumulation following explosive volcanic eruptions. The code uses a closed-form solution of the advection-diffusion equation, particle fall velocities that depend on local Reynold’s number, and stratified wind field to forecast tephra accumulation, expressed as kilogram per cubic meter, particle size distribution at specific locations from the vent, and maximum clast size expected as a function of distance from the vent. In practice, deposits of specific eruptions can be modeled if sufficient field data are available.


Partially funded by: NSF DRL 0940839 NSF EAR 0130602


Suzuki, T., 1983. A theoretical model for dispersion of tephra, in: D. Shimozuru and I. Yokoyama (eds) Arc Volcanism: Physics and Tectonics, Terra Scientific Publishing, Tokyo, 95-116.


Volentik, A.C.M., C. Bonadonna C. B. Connor, and L.J. Connor, 2010, Modeling tephra dispersal in absence of wind: 2450 BP eruption of Pululagua volcano (Ecuador), Journal of Volcanology and Geothermal Research Volentik, A.C.M., C. B. Connor, L.J. Connor, and C. Bonadonna, 2009, Aspects of volcanic hazard assessment for the Bataan nuclear power plant, Luzon Peninsula, Philippines. In: Volcanic and Tectonic Hazard Assessment for Nuclear Facilities. Edited by C.B. Connor, N.A. Chapman, and L.J., Connor. Cambridge University Press, 229-256. Lim, L.L., W.L. Sweatman, R. McKibben, and C.B. Connor, 2008. Tephra Fallout Models: The effect of different source shapes on isomass maps. Mathematical Geosciences, 40(2): 147-157. Byrne, M.A., A. G. Laing, and C. B. Connor, 2007. Predicting tephra dispersion with a mesoscale atmospheric model and a particle fall model: Application to Cerro Negro volcano, Journal of Applied Meteorology and Climatology, 46: 121-135. Connor, L.J., and Connor, C.B., 2006. Inversion is the key to dispersion: Understanding eruption dynamics by inverting tephra fallout. In: Mader, H.M., Coles, S.G., Connor, C.B., and Connor, L.J. (eds.) Statistics in Volcanology. Special Publications of IAVCEI 1. Geological Society, London, 231-242. Bonadonna, C., C.B. Connor, B.F. Houghton, L. Connor, M. Byrne, A. Laing, and T. Hincks, 2005. Probabilistic modeling of tephra dispersion: hazard assessment of a multi-phase eruption at Tarawera, New Zealand, Journal of Geophysical Research, 110 (B03203). Connor, C.B., B.E. Hill, B. Winfrey, N.M. Franklin, and P.C. LaFemina, 2001, Estimation of volcanic hazards from tephra fallout, Natural Hazards Review, 2: 33-42.

Cite this work

Researchers should cite this work as follows:

  • Connor, L., C. Connor, C. Bonadonna, L. Courtland, "Tephra2," http://vhub.org/contribtool/tephra2.
  • Costanza Bonadonna; Laura J Connor; Chuck B Connor; Leah Michelle Courtland (2014), "Tephra2," https://vhub.org/resources/tephra2.

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