Composite ground deformation pattern forerunning the 2004–2005 Mount Etna eruption

After the end of the 2002–2003 eruption, Mount Etna activity was characterized only
by gentle degassing at the summit craters and some earthquake swarms. Suddenly, an
eruption started on 7 September 2004 in complete absence of summit crater volcanic
activity, seismicity or seismic tremor, and ground deformation. This is the first time that
magma poured out passively without preeruptive and coeruptive volcanic and/or
geophysical phenomena. The primary key to understanding this event is represented by the
ground deformation pattern recorded through GPS measurements during the year
before the eruption. The ground deformation shows inflation superimposed by a
predominant eastward movement of the eastern sector at a rate never observed before
in a noneruptive period. The images from satellite radar interferometry confirmed this
pattern. The deformation field clearly shows that the maximum tension in the eastern
sector of the volcano caused the opening of the eruptive fracture which favored the
silent pouring out of already resident magma.

Acocella, V., B. Behncke, M. Neri, and S. D’Amico (2003), Link between
major flank slip and 2002– 2003 eruption at Mt. Etna (Italy), Geophys.
Res. Lett., 30(24), 2286, doi:10.1029/2003GL018642.
Aloisi, M., A. Bonaccorso, S. Gambino, M. Mattia, and G. Puglisi (2003),
Etna 2002 eruption imaged from continuous tilt and GPS data, Geophys.
Res. Lett., 30(23), 2214, doi:10.1029/2003GL018896.
Aloisi, M., A. Bonaccorso, and S. Gambino (2006), Imaging composite
dike propagation (Etna, 2002 case), J. Geophys. Res., 111, B06404,
doi:10.1029/2005JB003908.
Bonaccorso, A., and P. M. Davis (2004), Modeling of ground deformation
associated with recent lateral eruptions: Mechanism of magma ascent and
intermediate storage at Mt. Etna, in Etna Volcano Laboratory, Geophys.
Monogr. Ser., vol. 143, edited by A. Bonaccorso et al., pp. 293–306,
AGU, Washington, D. C.
Bonaccorso, A., M. Aloisi, and M. Mattia (2002), Dike emplacement forerunning
the Etna July 2001 eruption modeled through continuous tilt and
GPS data, Geophys. Res. Lett., 29(13), 1624, doi:10.1029/
2001GL014397.
Bonforte, A., and G. Puglisi (2003), Magma uprising and flank dynamics on
Mount Etna volcano, studied using GPS data (1994– 1995), J. Geophys.
Res., 108(B3), 2153, doi:10.1029/2002JB001845.
Bonforte, A., and G. Puglisi (2006), Dynamics of the eastern flank of
Mt. Etna volcano (Italy) investigated by a dense GPS network, J. Volcanol.
Geotherm. Res., 153, 357– 369.
Borgia, A., L. Ferrari, and G. Pasquare` (1992), Importance of gravitational
spreading in the tectonic and volcanic evolution of Mount Etna, Nature,
357, 231–235.
Borgia, A., R. Lanari, E. Sansosti, M. Tesauro, P. Berardino, G. Fornaro,
M. Neri, and J. B. Murray (2000), Actively growing anticlines beneath
Catania from distal motion ofMount Etna’s decollement measured by SAR
interferometry and GPS, Geophys. Res. Lett., 27, 3409–3412.
Bousquet, J. C., and G. Lanzafame (2004), The tectonics and geodynamics
of Mt. Etna: Synthesis and interpretation of geological and geophysical
data, in Etna Volcano Laboratory, Geophys. Monogr. Ser., vol. 143,
edited by A. Bonaccorso et al., pp. 29– 47, AGU, Washington, D. C.
Burton, M. R., et al. (2005), Etna 2004– 2005: An archetype for geodynamically-
controlled effusive eruptions, Geophys. Res. Lett., 32, L09303,
doi:10.1029/2005GL022527.
Cervelli, P., P. Segall, K. Johnson, M. Lisowski, and A. Miklius (2002),
Sudden aseismic fault slip on the south flank of Kilauea volcano, Nature,
415, 1014–1018.
Corsaro, R. A., and L. Miraglia (2005), Dynamics of 2004–2005 Mt. Etna
effusive eruption as inferred from petrologic monitoring, Geophys. Res.
Lett., 32, L13302, doi:10.1029/2005GL022347.
Dvorak, J. J., and D. Dzurisin (1997), Volcano geodesy: The search for
magma reservoirs and the formation of eruptive vents, Rev. Geophys.,
35(3), 343– 384.
Froger, J. L., O. Merle, and P. Briole (2001), Active spreading and regional
extension at Mount Etna imaged by SAR interferometry, Earth Planet.
Sci. Lett., 148, 245–258.
Gambino, S., A. Mostaccio, D. Patane`, L. Scarfı`, and A. Ursino (2004),
High-precision locations of the microseismicity preceding the 2002 –
2003 Mt. Etna eruption, Geophys. Res. Lett., 31, L18604, doi:10.1029/
2004GL020499.
Lo Giudice, E., and R. Rasa` (1992), Very shallow earthquakes and brittle
deformations in active volcanic areas: The Etnean region as an example,
Tectonophysics, 202, 257– 268.
Lundgren, P., and P. A. Rosen (2003), Source model for the 2001 flank
eruption of Mt. Etna volcano, Geophys. Res. Lett., 30(7), 1388,
doi:10.1029/2002GL016774.
Lundgren, P., P. Berardino, M. Coltelli, G. Fornaro, R. Lanari, G. Puglisi,
E. Sansosti, and M. Tesauro (2003), Coupled magma chamber inflation
and sector collapse slip observed with synthetic aperture radar
interferometry on Mt. Etna volcano, J. Geophys. Res., 108(B5), 2247,
doi:10.1029/2001JB000657.
Lundgren, P., F. Casu, M. Manzo, A. Pepe, P. Berardino, E. Sansosti, and
R. Lanari (2004), Gravity and magma induced spreading of Mount Etna
volcano revealed by satellite radar interferometry, Geophys. Res. Lett.,
31, L04602, doi:10.1029/2003GL018736.
McTigue, D. F. (1987), Elastic stress and deformation near a finite spherical
magma body: Resolution of the point source paradox, J. Geophys. Res.,
92, 12,931– 12,940.
Mogi, K. (1958), Relation between the eruptions of various volcanoes and
the deformations of the ground surface around them, Bull. Earthquake
Res. Inst. Univ. Tokyo, 36, 99– 134.
Neri, M., V. Acocella, and B. Behncke (2004), The role of the Pernicana
Fault System in the spreading of Mount Etna (Italy) during the 2002– 2003
eruption, Bull. Volcanol., 66, 417– 430, doi:10.1007/s00445-003-0322-x.
Nunnari, G., G. Puglisi, and F. Guglielmino (2005), Inversion of SAR data
in active volcanic areas by optimization techniques, Nonlinear Processes
Geophys., 12, 863–870.
Okada, Y. (1985), Surface deformation due to shear and tensile fault in halfspace,
Bull. Seismol. Soc. Am., 75, 1135– 1154.
Owen, S., P. Segall, M. Liswoski, A. Miklius, M. Murray, M. Bevis, and
J. Foster (2000a), January 30, 1997 eruptive event at Kilauea volcano,
Hawaii, as monitored by continuous GPS, Geophys. Res. Lett., 27(17),
2757– 2760.
Owen, S., P. Segall, M. Lisowski, A. Miklius, R. Denlinger, and M. Sako
(2000b), Rapid deformation of Kilauea volcano: Global Positioning System
measurements between 1990 and 1996, J. Geophys. Res., 105(B8),
18,983– 18,998.
Patane`, D., P. De Gori, C. Chiarabba, and A. Bonaccorso (2003), Magma
ascent and the pressurization of Mount Etna’s volcanic system, Science,
299, 2061– 2063.
Patane`, D., M. Mattia, and M. Aloisi (2005), Shallow intrusive processes
during 2002– 2004 and current volcanic activity on Mt. Etna, Geophys.
Res. Lett., 32, L06302, doi:10.1029/2004GL021773.
Puglisi, G., and A. Bonforte (2004), Dynamics of Mount Etna Volcano
inferred from static and kinematic GPS measurements, J. Geophys.
Res., 109, B11404, doi:10.1029/2003JB002878.
Puglisi, G., P. Briole, and A. Bonforte (2004), Twelve years of ground
deformation studies on Mt. Etna volcano based on GPS surveys, in Etna
Volcano Laboratory, Geophys. Monogr. Ser., vol. 143, edited by
A. Bonaccorso et al., pp. 321–341, AGU, Washington, D. C.
Rasa`, R., R. Azzaro, and O. Leonardi (1996). Aseismic creep on faults and
flank instability at Mt. Etna volcano, in Volcano Instability on the Earth
and Other Planets, edited by W. J. McGuire, A. P. Jones, and J. Neuberg,
Geol. Soc. Spec. Publ., 110, 179– 192.
Rust, D., and M. Neri (1996), The boundaries of large-scale collapse on the
flanks of Mount Etna, Sicily, in Volcano Instability on the Earth and
Other Planets, edited by W. J. McGuire, A. P. Jones, and J. Neuberg,
Geol. Soc. Spec. Publ., 110, 193– 208.
Rust, D., B. Behncke, M. Neri, and A. Ciocanel (2005), Nested zones of
instability in the Mount Etna volcanic edifice, Sicily, J. Volcanol.
Geotherm., 144, 137–153, doi:10.1016/j.jvolgeores.2004.11.021.
Thornber, C. R., C. Heliker, D. R. Sherrod, J. P. Kauahikaua, A. Miklius,
P. G. Okubo, F. A. Trusdell, J. R. Budahn, W. I. Ridley, and G. P. Meeker
(2003), Kilauea east rift zone magmatism: An episode 54 perspective,
J. Petrol., 44(9), 1525–1559.
Tiampo, K. F., J. B. Rundle, J. Fernandez, and J. O. Langbein (2000),
Spherical and ellipsoidal volcanic sources at Long Valley Caldera, California
using a genetic algorithm inversion technique, J. Volcanol.
Geotherm. Res., 102, 189– 206.
Tiampo, K. F., J. Fernandez, G. Gentzsch, M. Charco, and J. B. Rundle
(2004), Inverting for the parameters of a volcanic source using a genetic
algorithm and a model for magmatic intrusion in elastic-gravitational
layered Earth models, Comput. Geosci., 30(9 – 10), 985 – 1001,
doi:10.1016/j.cageo.2004.07.005.
Tibaldi, A., and G. Gropelli (2002), Volcano-tectonic activity along structures
of the unstable NE flank of Mt. Etna (Italy) and their possible
origin, J. Volcanol. Geotherm. Res., 115, 277– 302.