Dike emplacement forerunning the Etna July 2001 eruption modeled through continuous tilt and GPS data

Abstract

Late on the night of July 17, 2001, a lateral eruption started from the slopes of Mt. Etna. A 7 km long field of ground fractures opened between 13 and 20 July. The eruption ended on August 9, 2001 after emitting a lava volume of approximately 48 · 106 m3. A strong seismic swarm earthquake was recorded between July 12 and 17. The evolution leading up to the July crisis was monitored through continuous tilt and GPS measurements, which constrained the intrusion preceding the eruption in time, and inferred the position and geometry of the uprising dike. We modeled the marked ground deformation changes recorded in the days before the eruption onset. The result shows that a tensile crack with an opening dislocation of ca. 3 m, crossing the volcano edifice slightly southeast of the crater area, can explain the recorded deformation pattern. The location of the modeled tensile source fits the zone of the seismic swarm occurring during the magma uprising. The ground deformation pattern associated with the final uprising and its modeling suggest a very fast dike emplacement which appears different, both in terms of rapidity (only a few days) and source position, with respect to the sources modeled for the other lateral eruptions in the last twenty years.

Volatile-rich magma injection into the feeding system during the 2001 eruption of Mt. Etna (Italy): its role on explosive activity and change in rheology of lavas

“…The stable assemblage and thermodynamic properties of the resident magma were calculated at the following conditions: 1) T=990°C, according to phase equilibria between Mg-hastingsite amphibole and other phases in the system (Pompilio and Rutherford 2002;Viccaro et al 2006Viccaro et al , 2007; 2) P=200 MPa, based on aforementioned phase equilibria and the hypocentral depths (6 km b.s.l.) of the earthquake swarm that preceded the eruption of this magma (Bonaccorso et al 2002;Patanè Monaco et al 2005); 3) fO 2 at QFM buffer, in agreement with the literature data for most Etnean magmas (cf. Pompilio et al 1998).…”

“…1). The eruption was preceded by shallow seismic swarms totaling 2,600 earthquakes (Bonaccorso et al 2002;Patanè et al 2002;Monaco et al 2005). On July 12, a seismic swarm preceded the opening of fissures at the surface between 3,100 and 2,100 m (a.s.l.).…”

“…Modeling of the phase assemblage and proportions of phenocryst minerals in the system has been performed using MELTS (Ghiorso and Sack 1995;Asimow and Ghiorso 1998). Physical-chemical parameters were constrained by geochemical and geophysical data from literature (Bonaccorso et al 2002, Patanè et al 2002Monaco et al 2005;Viccaro et al 2006;Ferlito et al 2008). The reliability of the modeling was constrained by comparing the results with volcanological observations.…”

Magma convection and mixing dynamics as a source of Ultra-Long-Period oscillations

“…In the large majority of cases, in fact, the employed instruments do not cover such a frequency range (Scarpa 2001) or do not have enough temporal resolution. This is true at Mount Etna and Campi Flegrei where broadband seismic instruments have a cutoff frequency corresponding to about 40 s and long baseline tiltmeter data are recovered with a frequency of one every 10 min (Mount Etna; Bonaccorso et al 2002;Cannata et al 2009) or have just been set up and are still in the experimental phase (Campi Flegrei; R. Scarpa, personal communication). The resolving capability of GPS networks is of order several millimeters or larger (Bonaccorso et al 2002), still too low to detect ground oscillations with amplitude comparable to that emerging from the present simulations.…”

Thermal weakening of the carbonate basement under Mt. Etna volcano (Italy): Implications for volcano instability

“…dyke (Bonaccorso et al, 2002;Patanè et al, 2002) at about 3.5 km depth; however, structural and seismic evidence exclude a shallow connection between the summit and the peripheral magmatic systems . Since the connection between the summit and the peripheral magmatic systems is considered to be at deeper crustal levels Carbone et al, 2009), the peripheral dykes are likely to have traversed through rocks of the Hyblean Plateau previously unexposed to high temperatures.…”