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Simultaneous magma and gas eruptions at three volcanoes in southern Italy: An earthquake trigger?

¹Department 2: Physics of the Earth, Helmholtz Centre Potsdam, GFZ German Research Centre for Geoscience, Telegrafenberg, 14473 Potsdam, Germany
²Dipartimento Scienze Geologiche, Università Roma Tre, Largo S.L. Murialdo 1, 00146 Rome, Italy
³Istituto Nazionale di Geofisica e Vulcanologica (INGV), Catania, Piazza Roma 2, 95123 Catania, Italy

View larger version (42K): [in this window] [in a new window]   Figure 1. Shaded relief map of Sicily and Aeolian Islands. Tectonic strain orientation: black arrows show compression in western volcanic Aeolian Arc, white arrows show extension in eastern Aeolian Arc (after Billi et al., 2007). Circles are earthquake magnitude M > 1 epicenters from Advanced National Seismic System earthquake catalogue 2000–2005 (http://earthquake.usgs.gov/anss/), stars are mainshocks M > 5, Harvard centroid moment tensor solution is provided for Palermo M = 5.9 event. Note that four M > 5 earthquakes occurred, but two had depths >200 km (17 May 2001 [M = 5.2] and 5 May 2004 [M = 5.5]), while September 2002 earthquake and its aftershocks were shallow (<30 km). Earthquake main shocks and remotely triggered volcanoes investigated herein are shown with red symbols. Tectonic lines are from Billi et al. (2007). Ust—Ustica; Ali—Alicudi; Fil—Filicudi; S—Salina; Li—Lipari; V—Vulcano; Pan—Panarea; Str—Stromboli. Seismic stations at TOR (Tortorici) and AIO (Antillo).

View larger version (16K): [in this window] [in a new window]   Figure 2. Volcanic activity (red lines) shortly after largest earthquake and its aftershocks in September 2002. Same earthquake data as in Figure 1; magnitudes >5 are indicated by stars. a—Mount Etna; b—Panarea; c—Stromboli.

View larger version (20K): [in this window] [in a new window]   Figure 3. Synthetic seismograms showing east-west (E), north-south (N), and vertical components (Z). From these three components, we determined the pressure change (P, shown in red) as function of time. Pressure fluctuations reached ±10 kPa for Mount Etna and ± 8 kPa for the Panarea and Stromboli Island volcanoes.

View larger version (10K): [in this window] [in a new window]   Figure 4. Conceptual model of time (t)-strain () changes in the Panarea-Stromboli-Etna systems. Extensional tectonic strain built up in the long term, locally causing elevated pore pressure at hydrothermal and magmatic centers. Earthquake-induced short-term fluctuations exceeded the long-term signals. In the 2002 events, strain changes are similar to 10–20 yr of tectonic strain, but occurred within seconds.