High Detailed Lava Flows Hazard Maps by a Cellular Automata Approach - Simulation and Modeling Methodologies, Technologies and Application - page 87

was defined on the considered as a covering for Mt Etna, as shown in Figure 2. This
choice allowed to both adequately and uniformly cover the study area, besides consid-
ering a relatively small number of craters. Specifically, a subset of event classes which
define 6 different effusion rates probabilities, derived from historical events considered
in [17], were taken into account for each crater, thus resulting in a total of 25740 differ-
ent simulations to be carried out. Owing to the elevated number of SCIARA simulations
to be carried out, thanks to the adoption of Parallel Computing each scenario was simu-
lated for each of the vents of the grid. Simulations were performed on an 80-node Apple
Xserve Xeon-based cluster and were performed in ca. 10 days.
Lava flow hazard was then punctually evaluated by considering the contributions of
all the simulations which affected a generic cell in terms of their probability of oc-
currence. formally, if a given DEM cell (and thus, a CA cell) of co-ordinates ( x, y ) is
affected by n x,y ≤ N simulations, being N the overall number of performed simula-
tions, its hazard h x,y can be defined as the sum of the probabilities of occurrence of
involved lava flows, p e ( i ) ( i =1, 2, ..., n x,y ):

n x,y

h x,y = p e ( i )

(5)

i =1

The obtained lava flow hazard map resulting from these simulations and the applica-
tion of equation 5 is presented in Figure 3, and represents the probability that future
eruptions will affect the entire Etnean area.
Importantly, the methodology for the compilation of lava flows invasion hazard maps
here proposed provides for, as integrant part, a process for the verification of results. A
validation procedure was thus contemplated for the produced hazard map, consisting in
a technique which produces statistical indicators on which one can quantify the reliabil-
ity of the results and, therefore, assess whether the final product can be confidently used
for Civil Protection, for example, for setting in safety particularly vulnerable areas, and
for Land Use Planning. Refer to [17] for major details on the methodology validation
process.

4 Applications for Civil Defense and Land Use Planning

As shown previously, the described methodology permits the definition of general haz-
ard maps, as the one reported in Figure 3, which can give valuable information to Civil
Defense responsible authorities. However, further, more specialized applications can
be devised by considering that the SCIARA simulation model is integrated in a GIS
Geographic Information System) application that permits to take also into account the
effects of “virtual” embankments, channels, barriers, etc. In particular, the availability
of a large number of lava flows of different eruption types, magnitudes and locations
simulated for this study allows the instantaneous extraction of various scenarios. This is
especially relevant once premonitory signs indicate the possible site of imminent erup-
tions, and thus permitting to consider hazard circumscribed to a smaller area. An im-
portant Civil Defense oriented application regards the possibility to identify all source
areas of lava flows that are capable of affecting a given area of interest, such as a town or