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Modeling and forecasting tephra dispersion with TEPHRA2

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Monday, October 12, 2009, 4 pm

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This is a past event.

Chuck Connor
University of South Florida
Tampa, FL

TEPHRA2 is a parallel code written in C and MPI 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, usually 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 using TEPHRA2 and a nonlinear inversion method, the downhill simplex algorithm, to estimate best fit eruption parameters. I demonstrate wide applicability of TEPHRA2 with examples from Cerro Negro, Nicaragua (small volume basaltic eruption), Colima, Mexio (short-lived basaltic-andesite vulcanian eruption), and Chaiten, Chile (comparatively small volume Plinian eruption of rhyolite composition). In each case models of the eruption based on inversion of the deposit thickness and/or granulometry compares well with independent observations. An advantage of this inversion procedure is that it is possible to assign numerical uncertainty to estimates of deposit volume, eruption column height, eruption duration, and similar eruption input parameters.

Suggested Reading Material

Connor, C.B., B.E. Hill, B. Winfrey, N.M. Franklin, and P.C. LaFemina
Estimation of volcanic hazards from tephra fallout
Part 1 | Part 2

Bonadonna, C., C.B. Connor, B.F. Houghton, L. Connor, M. Byrne, A. Laing, and T. Hincks
Probabilistic modeling of tephra dispersal: Hazard assessment of a multiphase rhyolitic eruption at Tarawera, New Zealand

Hosts Erika Vye ( and Jarod Maggio (

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