Geoelectrica Vesubio

Geophysical tomography. The Vesuvius case-history

Imaging polar and dipolar sources of geophysical anomalies by probability
tomography. Part II: Application to the Vesuvius volcanic area
Paolo Mauriello 1 and Domenico Patella 2
1

Department of Science and Technology for Environment and Territory, University of Molise, Campobasso, Italy
(E-mail: mauriello@unimol.it)
2

Department ofPhysical Sciences, University Federico II, Naples, Italy
(E-mail: patella@na.infn.it)

ABSTRACT
In the previous part I, we have developed the generalized theory of the probability tomography method to image
polar and dipolar sources of a vector or scalar geophysical anomaly field. The purpose of the new method was to
improve the core-and-boundary resolution of the most probable buried sourcesof the anomalies detected in a
datum domain. In this paper, which constitutes the part II of the same study, an application of the new approach
to the Vesuvius volcano (Naples, Italy) is illustrated in detail by analyzing geoelectrical, self-potential and gravity
datasets collected over the whole volcanic area. The purpose is to get new insights into the shallow structure and
hydrothermalsystem of Vesuvius, and the deep geometry of the tectonic depression within which the volcano
grew.

INTRODUCTION
In the first part of this study (Mauriello and Patella,
2006), from now onward indicated with MP-I, we have
illustrated the theory of the 3D probability tomography,
under the assumption that any geophysical dataset can
be interpreted as the response of a double set of hiddensources, schematized as poles and dipoles. Source pole
and dipole occurrence probability functions (SPOP and
SDOP, respectively) were introduced to obtain a coreand-boundary imaging of the most probable sources of
the detected geophysical anomalies.
In this second part, the results from an application
to the Mt. Somma-Vesuvius volcano (Naples, Italy) are
presented. To avoid repetitions, allprevious equations
and figures needed to understand this application, will
be recalled referring to the numbering used in MP-I.
Geophysics is currently applied in volcanology to
define the physical and geometric features of a volcanic
apparatus and to study feeding and plumbing systems.
Mt. Somma-Vesuvius is among the most surveyed
active volcanoes in the world for the great concern due
to thehigh level of urbanization existing all around its
slopes, closest to the city of Naples. A comprehensive
collection of the most recent studies about the volcanic
structure and dynamics is given by Spera et al. (1998).
The geophysical evidences achieved so far indicate
that Vesuvius grew inside a depression of a carbonate
basement with normal crustal density, filled with less
densesediments. The shallower portion of the volcano
has been interpreted as a central plumbing system surrounded by slowly cooled dikes. The summit cone is

http://arxiv.org/physics/0602057

likely made of altered volcanics. Moreover, a high-tolow velocity and resistivity boundary estimated within
a 8-10 km depth range beneath the Vesuvius cone has
been assumed as the top of a magma chamber. Thoughnot yet geometrically and structurally well constrained,
these features indicate that Vesuvius is still to be considered a highly hazardous volcano.

Figure 1 A satellite map of the Vesuvius volcanic
district with localization of the self-potential and
gravity survey areas and the geoelectrical profiles.

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P.Mauriello and D.Patella

These results were got using standard modeling andinversion tools, except for the geoelectric, gravity and
self-potential data, which were analyzed by the original
formulation of the SPOP tomography (Patella, 1997;
Patella and Mauriello, 1999; Iuliano et al., 2002).
In the next sections, we give some new results from
a joint application of the SPOP and SDOP tomography
to the geoelectric, self-potential and gravity datasets on
Vesuvius....