Active tectonics of the Adriatic region from GPS and earthquake slip vectors

Abstract

To investigate the kinematics of the Adriatic region, we integrate continuous and episodic GPS measurements with Mw > 4.5 earthquake slip vectors selected from the Regional Centroid Moment Tensor catalogue. Coherent motion of GPS sites in the Po Valley, in Apulia, and in the Hyblean Plateau allows us to estimate geodetically constrained angular velocities for these regions. The predictions of the GPS‐inferred angular velocities are compared with the earthquake slip vectors, showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion. The remarkable consistency between geodetic, seismological, and geological evidence of active tectonics suggests that active deformation in the central Adriatic is controlled by the relative motion between the Adria and Apulia microplates. The microplates' angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses (1) that Apulia forms a single microplate with the Ionian Sea and possibly with the Hyblean region and (2) that Adria and Apulia rotate in such a way as to accommodate the Eurasia‐Nubia relative motion. We suggest that the present‐day microplate configuration follows a recent fragmentation of the Adriatic promontory that during the Neogene rigidly transferred the Africa motion to the orogenic belts that now surround the Adriatic region.

The anatomy of the 2009 L'Aquila normal fault system (central Italy) imaged by high resolution foreshock and aftershock locations

“…The current rate of extension is 4 mm/year [D'Agostino et al, 2008] and its orientation is consistent with available focal mechanism solutions [Anderson and Jackson, 1987;Montone et al, 2004], borehole breakout [Mariucci et al, 1999] and geological data [Lavecchia et al, 1994;Roberts and Michetti, 2004].…”

Tectonics, climate, and mountain topography

“…[52] Alps (Western) (WAL): We rely on the GPS results of Calais et al [2002a], and corroborated by several other studies [Calais et al, 2002a;D'Agostino et al, 2008;Serpelloni et al, 2005;Weber et al, 2010], which show essentially no present-day convergence across the western Alps, but extension and strike-slip movement parallel to the belt and internal deformation of it. This range may be a singular case, because active shortening is null but recent geological history shows that shortening across the range occurred during the Pliocene, and has apparently stopped since then.…”

Active faults and historical earthquakes in the Messina Straits area (Ionian Sea)

“…GPS measurements of Calabrian site motion relative to Apulia show systematic residuals directed towards the Ionian Sea. This suggests active crustal compression and an outward motion of the CA as a result of active subduction and shortening taken up in the accretionary wedge, eventually accommodated by long-term slip on the subduction interface (Gutscher et al, 2006;D'Agostino et al, 2008). The submerged portion of the CA consists of a NW thickening wedge of deformed sediments (Finetti 1982;Cernobori et al, 1996;Minelli and Faccenna, 2010) overlying, in the most external portion, NW dipping sediments and the basement.…”

“…1) is represented by a subduction complex bordered by two major structural features: the Malta escarpment to the SW and the Apulia escarpment to the NE. The CA accretionary wedge developed due to the SE-NW African/Eurasian plate convergence, presently occurring at a very slow rate (5 mm a −1 or less), according to recent Global Positioning System (GPS) studies (Calais et al, 2003;Reilinger et al, 2006;Serpelloni et al, 2007;D'Agostino et al, 2008;Devoti et al, 2008). Despite the very slow present-day plate convergence, subduction might be locally still active.…”

“…Slip vector in the African reference frame is indicated by a red arrow. In green are GPS vectors in the Apulian-fixed reference frame in which the motion of Calabria is parallel to the slip vector, suggesting the existence of active crustal compression as a result of subduction of the Ionian lithosphere beneath the Calabrian Arc (D'Agostino et al, 2008). The NW ward dipping subducting slab of the African Plate is represented by the yellow isodepth lines in the Tyrrhenian Sea spacing from 100 to 450 km depth (Selvaggi and Chiarabba, 1995).…”