Forearc extension and slow rollback of the Calabrian Arc from GPS measurements

Abstract

Here we describe the horizontal velocities of continuous GPS stations in the Calabrian Arc (CA) and surrounding regions. The appropriate reference frame to evaluate the crustal motion of the CA is considered by assessing the internal deformation and the relative motion of the crustal blocks in the foreland of the Apennines‐Ionian‐Maghrebides subduction system. We propose that the motion of CA relative to the subducting Ionian lower plate is most properly assessed by minimizing the GPS velocities in Apulia. In this reference frame the significant ≈2 mm/yr southeastward motion of the stations on the Ionian flank of the CA shows that the arc is still moving towards the trench in agreement with the observations of active shortening in the Ioanian wedge. This southeastward migration is associated to 1.4 ± 0.3 mm/yr E‐W extension of the forearc in northern Calabria, comparable with the seismic strain averaged in the last 500 years. The limited subaerial exposure decreases the resolution on locking of the subduction interface but the distribution and direction of crustal extension along the CA impose important constraints on geodynamic interpretations of the area.

Propagation of a lithospheric tear fault (STEP) through the western boundary of the Calabrian accretionary wedge offshore eastern Sicily (Southern Italy)

“…This is consistent with the very recent GPS measurements, that show that Calabria and the region NE Sicily still advances at significant rate of ~ 2-3 mm/yr towards the SE, in response to the SE-ward rollback of the Ionian slab (Figure 2) (D'Agostino et al, 2011;Devoti et al, 2011;Palano et al, 2012). Moreover, the tomographic images reveal a negative velocity anomaly at the SW edge of the subducting Ionian lithosphere, which was interpreted as lithospheric tear fault (Lucente et al, 1999;Wortel and Spakman, 2000;Piromallo and Morelli, 2003;Chiarabba et al, 2008;Neri et al, 2009).…”

“…Calabria with respect to a fixed Hyblean-Malta Plateau (Figure 2) (D'Agostino et al, 2011;Devoti et al, 2011;Palano et al, 2012). Furthermore, the formation of Mount Etna has been interpreted as a consequence of asthenospheric flow from Africa toward the Tyrrhenian, causing mantle flow through an asthenospheric window (Gvirtzman and Nur, 1999a;Faccenna et al, 2011).…”

Low slip rates and multimillennial return times for Mw 7 earthquake faults in southern Calabria (Italy)

“…This deformation, although much lower than in centralsouthern Apennine (2-3 mm/yr; Figure S1), documents that this portion of the CA is not migrating rigidly relative to Ionian lithosphere (i.e., at 2 mm/yr) [D'Agostino et al, 2011] but deforms internally. Moreover, here the extension driven by the CF parallels the regional dip direction of the Ionian slab and of the trenchward motion (Figures 1 and S1), a situation differing from the northern CA where the extension is oblique [Galli and Bosi, 2003;D'Agostino et al, 2011] (LF in Figures 1 and S1). Therefore, a possible geodynamic explanation for the crustal extension accommodated by the southern Calabria faults (CF and SF in Figures 1 and S1) and to the associated earthquakes is the still active eastward rollback of the Ionian lithosphere, with the measured geologic extension rate partly reflecting the present-day, residual Tyrrhenian back-arc opening.…”

“…CA formed during the Neogene as a consequence of NW subduction and SE trench rollback of a remnant of the Ionian lithosphere beneath Eurasia [Malinverno and Ryan, 1986;Patacca et al, 1990], and it is currently migrating relative to Ionian lithosphere with 2 mm/yr of convergence absorbed in the Ionian wedge ( Figure 1, inset A) [D'Agostino et al, 2011]. The subducting Ionian slab in the southern Tyrrhenian Sea is well depicted by both a Benjoff plain [Peterschmitt, 1956;Chiarabba et al, 2008] and by seismic tomography [Piromallo and Morelli, 2003].…”

Integrating geologic fault data into tsunami hazard studies

“…Chiarabba et al, 2008) and dips to the northwest. Convergence rates are in the order of 35 mm yr −1 in the Hellenic Arc (Reilinger et al, 2006) and 1-5 mm yr −1 in the Calabrian Arc (D' Agostino and Selvaggi, 2004;Devoti et al, 2008;Howe and Bird, 2010;Serpelloni et al, 2010;D'Agostino et al, 2011). Wide and thick accretionary wedges developed in both zones as a consequence of the subduction processes thereby deforming the thick sediment cover accumulated over time onto the Ionian crust.…”