Seafloor instability resulting from both tectonics and volcanism affects the Western Ionian Sea. The NEutrino Mediterranean Observatory-Submarine Network 1 (NEMO-SN1), deployed 25 km offshore eastern Sicily at 2,100 m water depth, records a variety of signals for geophysical and environmental long-term monitoring, including non-earthquake seismic signals that provide insights into the area’s geohazards. The signals analyzed for this paper are: (1) seismic signals associated with submarine landslides, (2) volcanic tremor, and (3) short duration events (SDEs). These seismic signals are analyzed together with pressure and hydrophone data to help identify their origins. Tectonic shifts can lead to submarine landslides. Volcanic tremor is the result of sustained pressure fluctuations, probably related to stress variations induced by magma movement. Increased tremor amplitudes recorded at NEMO-SN1 during lava fountain episodes from February to April 2013 suggest the presence of an east-southeast offshore location of the roots of Mt. Etna’s magma feeding system. SDEs are thought to result from hydrofracturing of carbonate outcroppings at the base of the Malta Escarpment that is possibly induced by changes in the stress field associated with magma movement.
Sgroi, T., S. Monna, D. Embriaco, G. Giovanetti, G. Marinaro, and P. Favali. 2014. Geohazards in the Western Ionian Sea: Insights from non-earthquake signals recorded by the NEMO-SN1 seafloor observatory. Oceanography 27(2):154–166, https://doi.org/10.5670/oceanog.2014.51.
Adam, J., C.D. Reuther, M. Grasso, and L. Torelli. 2000. Active fault kinematics and crustal stresses along the Ionian margin of southeastern Sicily. Tectonophysics 326:217–239, https://doi.org/10.1016/S0040-1951(00)00141-4.
Allard, P., B. Behncke, S. D’Amico, M. Neri, and S. Gambino. 2006. Mount Etna 1993–2005: Anatomy of an evolving eruptive cycle. Earth-Science Reviews 78:85–114, https://doi.org/10.1016/j.earscirev.2006.04.002.
Alparone, S., D. Andronico, L. Lodato, and T. Sgroi. 2003. Relationship between tremor and volcanic activity during the Southeast Crater eruption on Mount Etna in early 2000. Journal of Geophysical Research 108, 2241, http://dx.doi.org/10.1029/2002JB001866.
Argnani, A. 2009. Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab. Geological Society Special Publication 311:193–212, https://doi.org/10.1144/SP311.7.
Argnani, A., and C. Bonazzi. 2005. Malta Escarpment fault zone offshore eastern Sicily: Pliocene-Quaternary tectonic evolution based on new multichannel seismic data. Tectonics 24, TC4009, https://doi.org/10.1029/2004TC001656.
Ben-Avraham, Z., V. Lyakhovsky, and M. Grasso. 1995. Simulation of collision zone segmentation in the central Mediterranean. Tectonophysics 243:57-68, https://doi.org/10.1016/0040-1951(94)00191-B.
Bianca, M., C. Monaco, L. Tortorici, and L. Cernobori. 1999. Quaternary normal faulting in south-eastern Sicily (Italy): A seismic source for the 1693 large earthquake. Geophysical Journal International 139:370–394, https://doi.org/10.1046/j.1365-246x.1999.00942.x.
Bonaccorso, A. 1996. Dynamic inversion of ground deformation data for modeling volcanic sources (1991–93). Geophysical Research Letters 23:451–454, https://doi.org/10.1029/96GL00418.
Bonforte, A., and G. Puglisi. 2006. Dynamics of the eastern flank of Mt. Etna volcano (Italy) investigated by a dense GPS network. Journal of Volcanology and Geothermal Research 153:357–369, https://doi.org/10.1016/j.jvolgeores.2005.12.005.
Borgia, A., P.T. Delaney, and P. Denlinger. 2000. Spreading volcanoes. Annual Review of Earth and Planetary Sciences 28:539–570, https://doi.org/10.1146/annurev.earth.28.1.539.
Borgia, A., L. Ferrari, and G. Pasquarè. 1992. Importance of gravitational spreading in the tectonic and volcanic evolution of Mount Etna. Nature 37:231–235, https://doi.org/10.1038/357231a0.
Boschi, E., E. Guidoboni, G. Ferrari, D. Mariotti, G. Valensise, and P. Gasperini. 2000. Catalogue of strong Italian earthquakes from 461 BC to 1997. Annals of Geophysics, appendix to 43(4):609–868 (with database on CD-ROM).
Bowman, D.C., and W.S.D. Wilcock. 2014. Unusual signals recorded by ocean bottom seismometers on the caldera floor of Deception Island volcano, Antarctica. Antarctic Science 26:267–275, https://doi.org/10.1017/S0954102013000758.
Branca, S., M. Coltelli, and G. Groppelli. 2011. Geological evolution of a complex basaltic stratovolcano: Mount Etna, Italy. Italian Journal of Geoscience 130:306–317, https://doi.org/10.3301/IJG.2011.13.
Buskirk, R.E., C. Frohlich, G.V. Latham, A.T. Chen, and J. Lawton. 1981. Evidence that biological activity affects ocean bottom seismograph recordings. Marine Geophysical Researches 5:189–205.
Butler, R., A.D. Chave, F.K. Duennebier, D.R. Yoerger, R. Petitt, D. Harris, F.B. Wooding, A.D. Bowen, J. Bailey, J. Jolly, and others. 2000. Hawaii-2 observatory pioneers opportunities for remote instrumentation in ocean studies. Eos Transactions, American Geophysical Union 81(15):157–163, https://doi.org/10.1029/00EO00105.
Caplan-Auerbach, J., C.G. Fox, and F.K. Duennebier. 2001. Hydroacoustic detection of submarine landslides on Kilauea volcano. Geophysical Research Letters 28:1,811–1,813, https://doi.org/10.1029/2000GL012545.
Chadwick, W.W. Jr., S.L. Nooner, D.A. Butterfield, and M.D. Lilley. 2012. Seafloor deformation and forecasts of the April 2011 eruption at Axial Seamount. Nature Geoscience 5:474–477, https://doi.org/10.1038/ngeo1464.
Chierici, F., P. Favali, L. Beranzoli, A. De Santis, D. Embriaco, G. Giovanetti, G. Marinaro, S. Monna, L. Pignagnoli, G. Riccobene, F. Bruni, and F. Gasparoni. 2012. NEMO-SN1 (Western Ionian Sea, off Eastern Sicily): A cabled abyssal observatory with tsunami early warning capability. Pp. 130–137 in Proceedings of the 22nd (2012) International Offshore and Polar Engineering Conference, Rhodes, Greece, June 17–22, 2012.
Chouet, B. 1996. Long-period volcano seismicity: Its source and use in eruption forecasting, Nature 380:309–316, https://doi.org/10.1038/380309a0.
Chouet, B., P. Dawson, T. Ohminato, M. Martini, G. Saccorotti, F. Giudicepietro, G. De Luca, G. Milana, and R. Scarpa. 2003. Source mechanisms of explosions at Stromboli Volcano, Italy, determined from moment-tensor inversions of very-long-period data. Journal of Geophysical Research 108, 2019, https://doi.org/10.1029/2002JB001919.
Dalyander, P.S., B. Butman, C.R. Sherwood, R.P. Signell, and J.L. Wilkin. 2013. Characterizing wave- and current-induced bottom shear stress: US middle Atlantic continental shelf. Continental Shelf Research 52:73–86, https://doi.org/10.1016/j.csr.2012.10.012.
De Caro, M., S. Monna, F. Frugoni, L. Beranzoliand, and P. Favali. In press. Seafloor seismic noise at Central-Eastern Mediterranean sites. Seismological Research Letters.
Diaz, J., J. Gallart, and J. Gaspà. 2007. Atypical seismic signals at the Galicia Margin, North Atlantic Ocean, related to the resonance of subsurface fluid-filled cracks. Tectonophysics 433:1–13, https://doi.org/10.1016/j.tecto.2007.01.004.
Dziak, R.P., J.H. Haxel, D.R. Bohnenstiehl, W.W. Chadwick Jr., S.L. Nooner, M.J. Fowler, H. Matsumoto, and D.A. Butterfield. 2012. Seismic precursors and magma ascent before the April 2011 eruption at Axial Seamount. Nature Geoscience 5:478–482, https://doi.org/10.1038/ngeo1490.
Embriaco, D., G. Marinaro, F. Frugoni., S. Monna, G. Etiope, L. Gasperini, A. Polonia, F. Del Bianco, M.N. Çağatay, U.B. Ulgen, and P. Favali. 2014. Monitoring of gas and seismic energy release by multiparametric benthic observatory along the North Anatolian Fault in the Sea of Marmara (NW Turkey). Geophysical Journal International 196:850–866, https://doi.org/10.1093/gji/ggt436.
Favali, P., F. Chierici, G. Marinaro, G. Giovanetti, A. Azzarone, L. Beranzoli, A. De Santis, D. Embriaco, S. Monna, N. Lo Bue, and others. 2013. NEMO-SN1 abyssal cabled observatory in the Western Ionian Sea. IEEE Journal of Oceanic Engineering 38:358–374, http://dx.doi.org/10.1109/JOE.2012.2224536.
Favali, P., R. Person, C.R. Barnes, Y. Kaneda, J.R. Delaney, and S.-K. Hsu. 2010. Seafloor observatory science. In Proceedings of the OceanObs’09: Sustained Ocean. Observations and Information for Society. J. Hall, D.E. Harrison, and D. Stammer, eds, Venice, Italy, September 21–25, 2009, ESA Publication WPP-306, http://www.oceanobs09.net/proceedings/cwp/Favali-OceanObs09.cwp.28.pdf.
Fox, C.G., W.W. Chadwick Jr., and R.W. Embley. 2001. Direct observation of a submarine volcanic eruption from a sea-floor instrument caught in a lava flow. Nature 412:727–729, https://doi.org/10.1038/35089066.
Goslin, J., N. Louren, R.P. Dziak, D.R. Bohnenstiehl, J. Haxel, and J. Luis. 2005. Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone array. Geophysical Journal International 162:516–524, https://doi.org/10.1111/j.1365-246X.2005.02678.x.
Hirn, A., R. Nicolich, J. Gallart, M. Laigle, L. Cernobori, and ETNASEIS Scientific Group. 1997. Roots of Etna volcano in faults of great earthquakes. Earth and Planetary Science Letters 148:171–191, https://doi.org/10.1016/S0012-821X(97)00023-X.
Marani, M.P., F. Gamberi, G. Bortoluzzi, G. Carrara, M. Ligi, and D. Penitenti. 2004. Seafloor bathymetry of the Ionian Sea. Plate 3 in From Seafloor to Deep Mantle: Architecture of the Tyrrhenian Backarc Basin. M.P. Marani, F. Gamberi, and E. Bonatti, eds, Memorie Descrititive Carta Geologica d’Italia, vol. 44.
McGuire, W.J. 1996. Volcano instability: A review of contemporary themes. Pp. 1–23 in Volcano Instability on the Earth and other Planets. W.J. McGuire, A.P. Jones, and J. Neuberg, eds, Geological Society Special Publication, vol. 110.
Meletti, C., E. Patacca, and P. Scandone. 2000. Construction of a seismotectonic model: The case of Italy. Pure and Applied Geophysics 157:11–35, https://doi.org/10.1007/PL00001089.
Monna, S., G. Falcone, L. Beranzoli, F. Chierici, G. Cianchini, M. De Caro, A. De Santis, D. Embriaco, F. Frugoni, G. Marinaro, and others. 2014. Underwater geophysical monitoring for European Multidisciplinary Seafloor and water column Observatories. Journal of Marine Systems 130:12–30, https://doi.org/10.1016/j.jmarsys.2013.09.010.
Monna, S., F. Frugoni, C. Montuori, L. Beranzoli, and P. Favali. 2005. High quality seismological recordings from the SN1 deep seafloor observatory in the Mt. Etna region. Geophysical Research Letters 32, L07303, https://doi.org/10.1029/2004GL021975.
R Core Team. 2012. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria, http://www.lsw.uni-heidelberg.de/users/christlieb/teaching/UKStaSS10/R-refman.pdf.
Sartori, R., M.L Colalongo, G. Gabbianelli, C. Bonazzi, S. Carbone, P. Curzi, D. Evangelisti, M. Grasso, F. Lentini, S. Rossi, and L. Selli. 1991. Note stratigrafiche e tettoniche sul “Rise di Messina” (Ionio nord occidentale). Giornale di Geologia 53(2):49–64.
Scandone, P., E. Patacca, R. Radoicic, W.B.F. Ryan, M.B. Cita, M. Rawson, H. Chezar, E. Miller, J. McKenzie, and S. Rossi. 1981. Mesozoic and Cenozoic rocks from the Malta Escarpment (central Mediterranean). Bulletin of the American Association of Petroleum Geologists 65:1,299–1,319.
Sgroi, T., L. Beranzoli, G. Di Grazia, A. Ursino, and P. Favali. 2007. New observations of local seismicity by the SN1 seafloor observatory in the Ionian Sea, off-shore Eastern Sicily (Italy). Geophysical Journal International 169:490–501, https://doi.org/10.1111/j.1365-246X.2007.03348.x.
Sgroi, T., M. De Caro, N. Lo Bue, and P. Favali. 2013. Insights of the Mt. Etna volcanic activity through multiparametric data recorded by the NEMO-SN1 seafloor observatory. Mineralogical Magazine 77(5):2,184 (abstract), http://goldschmidt.info/2013/abstracts/finalPDFs/2184.pdf.
Sgroi, T., C. Montuori, R. Agrusta, and P. Favali. 2009. Low-frequency seismic signals recorded by OBS at Stromboli volcano (Southern Tyrrhenian Sea). Geophysical Research Letters 36, L04305, https://doi.org/10.1029/2008GL036477.
Sohn, R.A., J.A. Hildebrand, S.C. Webb, and C.G. Fox. 1995. Hydrothermal microseismicity at the Megaplume site on the southern Juan de Fuca Ridge. Bulletin of the Seismological Society of America 85:775–778.
Sultan, N., V. Riboulot, S. Ker, B. Marsset, L. Géli, J.B. Tary, F. Klingelhoefer, M. Voisset, V. Lanfumey, J.L. Colliat, and others. 2011. Dynamics of fault-fluid-hydrate system around a shale-cored anticline in deepwater Nigeria. Journal of Geophysical Research 116, B12110, https://doi.org/10.1029/2011JB008218.
Tary, J.B., L. Géli, C. Guennou, P. Henry, N. Sultan, M.N. Çağatay, and V. Vidal. 2012. Microevents produced by gas migration and expulsion at the seabed: A study based on sea bottom recordings from the Sea of Marmara. Geophysical Journal International 190:993–1,007, https://doi.org/10.1111/j.1365-246X.2012.05533.x.
Tinti, S., A. Maramai, and L. Graziani. 2004. The new catalogue of Italian tsunamis. Natural Hazards 33:439–465, https://doi.org/10.1023/B:NHAZ.0000048469.51059.65.
Tolstoy, M., E.T. Baker, D.J. Fornari, K.H. Rubin, T.M. Shank, F. Waldhauser, D.R. Bohnenstiehl, D.W. Forsyth, R.C. Holmes, B. Love, and others. 2006. A sea-floor spreading event captured by seismometers. Science 314:1,920–1,922, https://doi.org/10.1126/science.1133950.
Tolstoy, M., F.L. Vernon, J.A. Orcutt, and F.K. Wyatt. 2002. Breathing of the seafloor: Tidal correlations of seismicity at Axial volcano. Geology 30:503–506, https://doi.org/10.1130/0091-7613(2002)030<0503:BOTSTC>2.0.CO;2.
Villaseñor, A., H.M. Benz, L. Filippi, G. De Luca, R. Scarpa, G. Patanga, and S. Vinciguerra. 1998. Three-dimensional P-wave velocity structure of Mt. Etna, Italy. Geophysical Research Letters 25:1,975–1,978, https://doi.org/10.1029/98GL01240.
Webb, S.C. 1998. Broadband seismology and noise under the ocean. Reviews of Geophysics 36:105–142, https://doi.org/10.1029/97RG02287.
Wilcock, W.S.D. 2001. Tidal triggering of microearthquakes on the Juan de Fuca Ridge. Geophysical Research Letters 28:3,999–4,002, https://doi.org/10.1029/2001GL013370.
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