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Figure 1 | Journal of Applied Volcanology

Figure 1

From: Operational eruption forecasting at high-risk volcanoes: the case of Campi Flegrei, Naples

Figure 1

Schematic representation of the BET_EF model’s settings (Marzocchi et al.2008). In panel A, the three nodes of the Event Tree are represented. At each node, a Bayesian inference scheme is performed assuming a Beta distribution for the probability, both for the analysis of anomalies (panel B) and for the background analysis (panel C). BET_EF automatically switches between these two regimes, based on the observed state of unrest (P unrest in panel B). During unrest episodes, the model is based on the analysis of monitoring anomalies (panel B), and it is set through the parameters T 1, T 2and w i , thresholds and weight of each monitoring measure, respectively. On the left, an example of fuzzy threshold is reported, where in x-axis the possible values for the parameter are reported, while in the y-axis is represented the degree of truth of the statement ’the parameter is anomalous’, given a measurement equal to x. On the right, the basic principles of the transformation from anomalies to probabilities are reported; Bayesian inference is performed on the parameters a and b. The background assessment is based on Bayesian inference on probabilities (panel C), where theoretical models set prior distributions (through the average Λ and the equivalent number of data Θ), updated with the available past data (through the number of successes y and of trials n). More details can be found in the text and in Marzocchi et al. (2008).

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