The Adriatic region: an independent microplate within the Africa-Eurasia collision zone

indent.3in We use Global Positioning System measurements at 30 sites to study crustal motion in the Adriatic region (central Mediterranean), alternately viewed as a promontory of North Africa or as a microplate within the Africa-Eurasia plate boundary.

We employ publicly available GPS observations made stations of the European Reference Permanent Network (EUREF) and the Italian Space Agency (ASI) continuous GPS networks to estimate deformation in the Adriatic region. We analyze the data using the GAMIT/GLOBK software. To improve the realization of a stable reference frame for the velocity solution, additional sites from the International GPS Service (IGS) and EUREF networks are included through the publicly available global regional loosely constrained solutions performed by the Scripps Orbit and Permanent Array Center (SOPAC). All together, our solution includes data spanning 4 years from 106 stations, including 44 in the Mediterranean area. We incorporate 23 additional sites from McCluski et al. [2000] to resolve the deformation in the Eastern Mediterranean and Caucasus.

Preliminary motions (1999-2002), relative to stable Eurasia, show a north-westward motion (N 24+/-5 W) at 5+/-1 mm/yr for stations located on the northern edge of the African plate. Sites in Corsica and northwestern Italy show no significant deformation, while the stations close to the Adriatic sea are characterized by a north-eastward motion (N 24+/-5 E) at 5+/-1 mm/yr. Stations located on the eastern edge of the Adriatic Sea move in the same direction (N 21+/-8 E) at a somewhat slower rate (3+/-1 mm/yr). The northward displacement (N 3+/-8 E at 3+/-1 mm/yr) of sites in the southern Italian peninsula may reflect a transition zone between the African plate and the Adriatic region.

To test the competing tectonic models proposed, we develop a block model of regional deformation that accounts for plate angular velocities and strain accumulation on plate boundary faults. The results suggest that an independent microplate model provides a better explanation for most of the deformation observed the Mediterranean area. In particular, this model correctly reproduces the NE motion of the Adriatic region, the motion of the Anatolian and Aegean plates in the eastern Mediterranean, and the NW motion of the African plate.