The Evaluation of Volcanic Risk in the Campi Flegrei Area


Largely based on Scandone and D'Andrea, 1995

The Risk is defined as the product (UNESCO, 1972, Fournier d'Albe, 1979):
 

Risk = (Value) x (Vulnerability) x (Hazard) (1)


Where the Value is the number of lives or the monetary value of goods at risk in a volcanic area; the Vulnerability is the percentage of lives or goods likely to be lost because of a given volcanic event; and the Hazard is the probability that a certain area be invested by a certain volcanic phenomenology.
The Hazard Evaluation
We hypothesizes that the eruptions of Campi Flegrei of such a size to produce substantial damage (VEI=3,4,5) follow a Poisson distribution (Wickmann, 1966). We considered only three classes of VEI likely to produce risk to human life at Campi Flegrei, namely those with VEI3 3.
VEI = 3: also defined as violent strombolian, are those eruptions like the one of 1538 that often caused some casualties.
VEI = 4 : also defined as sub-plinian are those eruptions as the ones of Averno or Agnano-Monte Spina. These eruptions are likely to produce extensive damages and casualties within the Campi Flegrei area.
VEI = 5-6: also defined as plinian are those eruptions like the Pomici Principali or Tufo Giallo Napoletano, likely to cause extensive damages and casualties also in areas outside the Campi Flegrei.
The associated probabilities of occurrence of at least one eruption, in ten years, are:

P3(>=1,10) = 0.0104

P4(>=1,10) = 0.0045

P5(>=1,10) = 0.0019

P6(>=1,10) = 0.0008

The risk for life loss derives mostly by the opening of vents and invasion of pyroclastic flows and surges. The opening of vents will cause different effects depending on the urbanization of the area. So we have evaluated the effect of different probability of opening of vents in the different areas of the caldera. In a way similar to that of Vesuvius we made a classification of the cities in the area according to their risk for human lives.
 
 

figure 1 - Classification of cities in the phlegrean area according to their risk
The cities with higher risk are those of Pozzuoli and Naples with a risk higher than tose caused by Vesuvius on its surrounding towns.
 
figure 2 - Map of volcanic risk Risk of Campi Flegrei

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