Publication Date:
2017-04-04
Description:
A general methodology of pyroclastic fall hazard assessment is proposed on the basis
of integrated results of field studies and numerical simulations. These approaches result in
two different methods of assessing hazard: (1) the ‘‘field frequency,’’ based on the
thickness and distribution of past deposits and (2) the ‘‘simulated probability,’’ based on
the numerical modeling of tephra transport and fallout. The proposed methodology mostly
applies to volcanoes that, by showing a clear correlation between the repose time and the
magnitude of the following eruptions, allows the definition of a reference ‘‘maximum
expected event’’ (MEE). The application to Vesuvius is shown in detail. Using the field
frequency method, stratigraphic data of 24 explosive events in the 3–6 volcanic
explosivity index range in the last 18,000 years of activity are extrapolated to a regular
grid in order to obtain the frequency of exceedance in the past of a certain threshold value
of mass loading (100, 200, 300, and 400 kg/m2). Using the simulated probability method,
the mass loading related to the MEE is calculated based on the expected erupted
mass (5 1011 kg), the wind velocity profiles recorded during 14 years, and various
column heights and grain-size populations. The role of these factors was parametrically
studied performing 160,000 simulations, and the probability that mass loading exceeded
the chosen threshold at each node was evaluated. As a general rule, the field frequency
method results are more reliable in proximal regions, provided that an accurate database of
field measurements is available. On the other hand, the simulated probability method
better describes events in middle distal areas, provided that the MEE magnitude can be
reliably assumed. In the Vesuvius case, the integration of the two methods results in a new
fallout hazard map, here presented for a mass loading value of 200 kg/m2.
Description:
Published
Description:
2063-2083
Description:
3V. Dinamiche e scenari eruttivi
Description:
JCR Journal
Description:
open
Keywords:
pyroclastic flows, numerical simulations
;
04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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