Newly acquired high-resolution, low-altitude aeromagnetic data over Vulcano Island and Southwestern Lipari in
the Southern Tyrrhenian Sea resolve the major volcanic features in the area associated with the past and present
activity. The magnetic character changes in amplitude and frequency from south-east to north-west. The Primordial
Vulcano, the Lentia Complex, the Piano Caldera units, the Fossa Caldera deposits, and the currently active
La Fossa cone and Vulcanello represent the main volcanic phases on Vulcano Island. They show a distinct
magnetic anomaly pattern, whereas prior to this survey, no magnetic signatures of these features were found

Chiappini, M.

De Ritis, R.

Motschka, K.

Supper, R.

Earth-prints Repository

1803
ANNALS  OF  GEOPHYSICS, VOL.  47, N.  6, December  2004
Mailing address: Dr. Riccardo De Ritis, Istituto Nazio-
nale di Geofisica e Vulcanologia, Via di Vigna Murata 605,
00143 Roma, Italy; e-mail: deritis@ingv.it
Key  words aeromagnetic data – magnetic anom-
alies – geomagnetism – Vulcano
1. Introduction
The Aeolian Arc, in the Southern Tyrrhen-
ian Sea, is characterized by active volcanism,
which may threaten population safety and ac-
tivities. An international activity has been
launched, aimed at investigating these highly
hazardous areas by means of integrated multi-
disciplinary geophysical studies. The purpose
of magnetic surveying is, in fact, to identify the
shallow geological components and the crustal
contribution of the Earth’s magnetic field.
When devoted to the definition of magnetic
fields, likely generated by spatial variations in
the magnetization of crustal rocks, magnetic
anomaly maps are produced to show this con-
tribution. By means of the survey described in
the present paper we highlight the lateral varia-
tion of magnetizations of the shallow crustal
rocks, computing the magnetic anomaly field.
An initial approach was conducted in cooper-
ation between the Geological Survey of Austria
and the Istituto Nazionale di Geofisica e Vul-
canologia of Rome, acquiring high-resolution air-
borne geophysical data over Vulcano Island. Vul-
cano is located in the southern sector of the Aeo-
lian volcanic district, and lies along a NNW-SSE
graben-like structure, approximately parallel to
the strike-slip «Tindari-Letoianni» Fault (Barberi
et al., 1994). The airborne survey, conducted by
means of a locally hired Squirrel AS-350 helicop-
ter, also partially covered the western side and the
submerged flanks of Lipari Island. The aim of the
present paper is to image the crustal structure of
the area by means of magnetic anomaly data, to
characterize the magnetic sources associated with
the various Volcanic cycles.
In addition to aeromagnetic data laser al-
timetry and gamma ray data were also collect-
ed. We focus our attention on processing the
magnetic data to develop the anomaly pattern
of the surveyed area and perform mathematical
analysis and data enhancement.
Aeromagnetic anomaly images of Vulcano
and Southern Lipari Islands 
(Aeolian Archipelago, Italy)
Robert Supper (1), Riccardo De Ritis (2), Klaus Motschka (1) and Massimo Chiappini (2)
(1) Geological Survey of Austria and University of Vienna, Vienna, Austria
(2) Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy
Abstract
Newly acquired high-resolution, low-altitude aeromagnetic data over Vulcano Island and Southwestern Lipari in
the Southern Tyrrhenian Sea resolve the major volcanic features in the area associated with the past and present
activity. The magnetic character changes in amplitude and frequency from south-east to north-west. The Pri-
mordial Vulcano, the Lentia Complex, the Piano Caldera units, the Fossa Caldera deposits, and the currently ac-
tive La Fossa cone and Vulcanello represent the main volcanic phases on Vulcano Island. They show a distinct
magnetic anomaly pattern, whereas prior to this survey, no magnetic signatures of these features were found.
1804
Robert Supper, Riccardo De Ritis, Klaus Motschka and Massimo Chiappini 
The whole Tyrrhenian Sea was previously in-
vestigated by means of oceanographic campaigns
between 1965 and 1972 (Allan and Morelli,
1971). The cruises acquired bathymetric, gravity
and magnetic data. Chiappini et al. (2000) re-
processed the magnetic data set and compiled a
regional magnetic anomaly map at sea level.
As far as aeromagnetic data are concerned,
previous surveys in the Southern Tyrrhenian
Sea were performed by the Italian national oil
company (Agip) in the late 1970’s. Agip ac-
quired total field magnetic data at an altitude of
4800 ft (1500 m), and published a grid with an
average spacing of 2.5 km (Agip Spa, 1981).
2. Acquisition and processing
The airborne survey covered the entire Vul-
cano Island and partially the western side and
the submerged flanks of Lipari. An optically-
pumped magnetometer acquired the total inten-
sity of the Earth’s magnetic field at a varying
barometric height, which provided a minimum
terrain clearance of about 50 m above the high-
est peaks. Due to the rugged topographic con-
ditions, however, an average clearance was
maintained around 150 m.
The magnetic sensor was towed about 30 m
below the helicopter. The ground-based equip-
ment consisted of a magnetic base station
recording the Earth magnetic field variations
for the entire duration of the survey flights. The
magnetic base station was deployed on the Is-
land, and recorded data at 1 Hz.
The aeromagnetic survey was conducted at
250 m line spacing with tie lines at an average
of 3000 m apart. Figure 1 shows the distribution
of the aeromagnetic profiles, as well as the lo-
cation of the magnetic base station. The towed-
bird magnetometer acquired data at 10 Hz. GPS
receiver was used for precise survey navigation.
Recording of flight altitude was assured by ac-
quisition of laser altimeter data at 0.3 Hz. All
magnetic and pseudorange navigation data
were recorded on a PC-based data acquisition
system on board the helicopter.
Data were de-spiked and each measurement
profile was visually inspected. The base station
data were used to remove the diurnal variation
Fig. 1. Distribution of the aeromagnetic profiles
over Vulcano Island and the southwestern flank of Li-
pari. The symbol 5 indicates the position of the mag-
netic base station. In the inset, the location of the sur-
vey area in the Southern Tyrrhenian Sea is indicated.
of the Earth’s magnetic field from the aeromag-
netic data. The survey was then reduced to a
common geomagnetic epoch using the follow-
ing equation:
1805
Aeromagnetic anomaly images of Vulcano and Southern Lipari Islands (Aeolian Archipelago, Italy)
Fig. 2. Shaded-relief aeromagnetic anomaly map of Vulcano and Southwestern Lipari.
F F F F. .s bs s
t
bs
t99 7 99 7= + -^ h
where Fst is the magnetic field (nT) acquired
during the survey at time t at point s; Fbst is the
value observed at the same time t at the base
station; F .bs99 7 is the value at the base station at
1999.7 and F .s99 7 is the value at the same point s
reduced to 1999.7.
To compute the magnetic anomaly field, data
were corrected using the Italian Geomagnetic
Reference Field (ItGRF) (Molina and De Santis,
1987; De Santis et al., 2003). This model, de-
spite having the same spatial gradients as IGRF,
is more constrained by the secular variation ob-
served at L’Aquila geomagnetic observatory.
Crossover analysis between profiles and tie
lines showed a few leveling errors, which were
statistically adjusted in a similar fashion as de-
scribed in Chiappini et al. (2000). A 60 m cell
grid then was produced as shown in fig. 2,
1806
Robert Supper, Riccardo De Ritis, Klaus Motschka and Massimo Chiappini 
where we applied shading algorithms to artifi-
cially illuminate the anomalies, emphasizing
those that are perpendicular or oblique to the di-
rection of illumination.
3. Aeromagnetic anomalies
The magnetic anomaly pattern of Vulcano
and Southeastern Lipari shows both short and
long wavelength anomalies. While the former
are associated with variations of magnetization
of shallow rocks, the latter may likely reflect
the regional character of tectonic features or
may be caused by bodies deeper than the out-
cropping volcanic structure. Superimposing the
magnetic anomaly grid to the digital elevation
model of Lipari and Vulcano Islands and the
surrounding bathymetry, facilitates the identifi-
cation of magnetic anomaly features in relation
Fig. 3. Aeromagnetic anomaly field superimposed on the shaded-relief image of the digital elevation model
and surrounding bathymetry. 
1807
Aeromagnetic anomaly images of Vulcano and Southern Lipari Islands (Aeolian Archipelago, Italy)
to possible shallow sources. This is clearly im-
aged in fig. 3. For example, in the off shore sec-
tor, northwest of Vulcano, a round positive
anomaly is well resolved (VE in fig. 4). It
seems to be associated with an isolated relief
identified by Gabbianelli et al. (1991) by means
of seismic profiles, and interpreted as eccentric
volcanic edifices, and clearly identified with the
digital elevation model. 
The southwestern flank of Vulcano is char-
acterized by a high amplitude, NW-SE trending
linear positive anomaly, which runs approxi-
mately parallel to the coast line. This anomaly
also borders the southwestern margin of the
«Primordial Vulcano» as shown in fig. 4 and in
the geological map in fig. 5. This truncated
composite cone forms the oldest (120 to 100
kyr) part of the Island. 
Fig. 4. Major geomorphologic and volcanic features identified by the magnetic anomaly field. VE – off shore vol-
canic edifice; LF – sequence of lava flows; R1 – Piano Caldera volcanic rim; FS – sub-circular negative magnetic
anomaly; LC – La Fossa Cone; R2 – La Fossa Caldera volcanic rim; LT – Lentia Complex; VU – Vulcanello.
1808
Robert Supper, Riccardo De Ritis, Klaus Motschka and Massimo Chiappini 
Once the primordial volcano collapsed, a
subsequent eruption phase which occurred until
20 kyr emplaced the Piano Caldera Units (De
Astis et al., 1997). The volcanic rim (indicated
with R1 in fig. 4) presents a distinct magnetic
signature having its highest amplitude values in
the southwestern part. South-east of R1 a re-
markable magnetic anomaly feature, labeled LF
in fig. 4 and extending in the offshore sector,
could be related to a sequence of lava flows not
completely outcropping. In the north-western
part of the Island, a high-amplitude positive
anomaly seems to be associated with the Lentia
Complex (LT in fig. 4), which is a remnant of a
larger volcanic structure formed between 24
and 15 kyr (fig. 5) (Barberi et al., 1994).
Observe in the area of La Fossa a circular
positive anomaly overlapping with the volcanic
rim R2 (fig. 4). La Fossa caldera consists of
volcanic units erupted between 15 and 8 kyr ap-
proximately, being therefore a later volcanic
phase (De Astis et al., 1997). Within R2, a low-
amplitude, short-wavelength negative anomaly
(FS) surrounds a magnetic high, associated
with the edifice of La Fossa cone (LC in fig. 4).
La Fossa cone is an active volcanic edifice ex-
tending 391 m high, located approximately in a
central position with respect to the caldera.
Formed during the last 6 kyr, the cone produced
the last eruption in 1880-1890, as reported by
Frazzetta et al. (1983, 1984). 
The northernmost structure of the Island is
called Vulcanello. Indicated in fig. 4 with VU,
Vulcanello is a composite lava platform, formed
as a new Island in 183 B.C. By means of ash ac-
cumulation due to successive eruptions in the 6th
Fig. 5. Geological map of Vulcano Island, modified from De Astis et al. (1997), showing the six volcanic units.
1809
Aeromagnetic anomaly images of Vulcano and Southern Lipari Islands (Aeolian Archipelago, Italy)
and 16th centuries A.D., it was later connected to
the main Island. The lava platform is well re-
solved by the aeromagnetic image with a posi-
tive long-wavelength pattern.
Moreover the region extending between the
south western side of Lipari and a narrow strip
of sea in front of this Island is characterized by
extremely low values of the anomaly magnetic
field (−800 nT). A possible reason for such
anomaly values could be related to a negative
part of an induced dipolar field whose positive
counterpart would be the high-amplitude anom-
aly situated west of it. Alternatively these values
could be related to remanent magnetization of a
body cooled during a reverse-polarity chron.
The latter interpretation seems to be far from re-
ality because the Aeolian volcanism took place
entirely in the present Brunes chron. It turns out
that an extension of the survey in the remaining
part of Lipari Island to better understand the
presence of this large negative anomaly area is
worthwhile.
Fig. 6. Upward continued magnetic anomaly map (1500 m).
1810
Robert Supper, Riccardo De Ritis, Klaus Motschka and Massimo Chiappini 
As previously mentioned, existing aeromag-
netic data in the study area belong to an old sur-
vey conducted in the late 1970’s by Agip (Agip
Spa, 1981). The regional character and the differ-
ent acquisition altitude of the Agip map do not re-
solve the volcanic features we identified in detail.
We attempted to compare our anomaly field with
the Agip data set. Observe in fig. 6 the upward
continued map to 1500 m. This image clearly
shows long-wavelength features, as well as a re-
markable similarity with the Agip map (Barberi
et al., 1994).
4. Conclusions
A high-resolution shaded relief total intensi-
ty, magnetic anomaly map was obtained after a
helicopter-borne aeromagnetic survey over Vul-
cano Island. The anomaly field is characterized
by a wide range of amplitudes and wavelengths.
The main stages of volcanic activity in the area
are investigated by the new data set: the Primor-
dial Vulcano, the Piano Caldera units older than
20 kyr, the Lentia Complex formed between 24
and 15 kyr, the Fossa Caldera deposits and vol-
canic units emplaced between 15 and 8 kyr, the
currently active La Fossa cone, and Vulcanello.
The short-wavelength, high-amplitude anom-
alies located in the center of «Piano Caldera» and
in the center of «La Fossa Caldera» respectively
lie along the SE-NW direction which is the main
direction of the tectonic features of this region,
parallel to the «Tindary Letojanni» Fault which
develops more to the south in the northern part of
Sicily. This orientation coincides with the direc-
tion of the migration of volcanism in the Island.
Moving from south east of Vulcano to north west
the volcanism becomes younger.
Acknowledgements
This work was supported by the European
Commission, Contract ENV4-CT97-0697 «Elec-
tromagnetic and Potential Field Integrated Tomo-
graphies Applied to Volcanic Environments -
TOMAVE» and by the Austrian Science Founda-
tion, contract P15515-TEC «Improved Model-
ling and Interpretation of Complex Geophysical
Data Applied to the Eolian Volcanic Province»
(COMVOLC). Additional financial support was giv-
en by the Geological Survey of Japan, by Istituto
Nazionale di Geofisica e Vulcanologia, Dottorato
di Ricerca in Geofisica – University of Bologna
and the Austrian Exchange Service (ÖAD). We
would further like to thank Maria Teresa Pareschi
for providing the compilation of bathymetric da-
ta for the Eolian Islands.
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(received February 5, 2004;
accepted November 10, 2004)


Aeromagnetic anomaly images of Vulcano and Southern Lipari Islands (Aeolian Archipelago, Italy)

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Aeromagnetic anomaly images of Vulcano and Southern Lipari Islands (Aeolian Archipelago, Italy)

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