IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3P1_4C-O10

Room A6

Date/Time: July 23 15:30-15:45

Volcanic eruption durations: Forecasts and controls.
Leanne S Gunn1 , Steve Blake1 , Chris Jones2 , Hazel Rymer1
1

Environment Earth and Ecosystems, The Open University, England, 2 Mathematics and Statistics, TheOpen University, England
E-mail: leanne.gunn@open.ac.uk

During volcanic eruptions a question commonly asked is "How long will the eruption last?" To help answer this, wedevelop means of forecasting the eventual end of a volcanic eruption using statistical and physical approaches.

Ideally we would consider a period of continuous magma effusion as the basic building block of an eruption. Dueto the nature of volcanic eruptions and the quality of historical records the start and/or end date of an eruption canbe ambiguous, so some eruption durations carry an uncertainty of up to several days or weeks whereas others
are known to a precision of less than one day. Short breaks in activity were dealt with by treating eruptive phases
separated by periods of inactivity of less than 10 days as belonging to the same eruption.

Using this method we have critically assessed the literature and compiled datasets of historic eruption durations
for Piton de la Fournaise (Indian Ocean), the flank eruptions of Mt Etna (Italy) and for 7 Icelandic volcanic systems.
We present a statistical forecasting tool, which models the distribution of historic eruption durations within adataset, and uses survival analysis to give the probability of a future eruption exceeding a specified duration. Such
forecasts could be useful for emergency response planning prior to an eruption, providing insight into the likely timescale of the scenario being considered. The method also allows the probability of exceeding a specified duration
to be calculated in cases where an eruption has already been occurring for a known amount of time. To assess
the effect of duration uncertainty on the forecasted results the model has been run using maximum and minimum
possible eruption durations with results showing an insignificant difference.

We also present a comparative study of the distribution of eruption durations for the datasets compiled.
Results indicate a predominance of shorter eruptions at Piton de la Fournaise, and longer eruptions at Hekla(Iceland). For an individual eruption, the final duration can be considered to be a function of the volume of material
available and the physical parameters controlling the rate at which this material is erupted i.e. magma viscosity,
conduit radius, conduit height etc. The unique distribution of eruption durations at each volcano can then beinterpreted to be a result of the range and distribution of the possible volumes and values for these parameters,
which are specific to the volcano itself. Recognition of these leading controls on eruption duration could underpin
the development of a physical model to forecast future eruption durations.

Such a model could be refined

throughout the early stages of an eruption, accounting for the physical properties that the eruption demonstrates,
thus providing a forecasting tool that includes more information than the previously mentioned statistical model.
Both approaches show great promise for their application in real life situations.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

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