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Adria microplate motion and active deformation of the Dinarides - inferences from Global Positioning System (GPS) data

We analyze a joint regional network of ~100 GPS sites spanning across the eastern margin of the Adriatic from Italy to southern Croatia, and covering the geodynamic units of the Southern Alps, the Adriatic microplate proper (Istria), the Dinarides, the Eastern Alps and the Pannonian Basin. Dataset consists predominately of high-precision survey-type GPS measurements that were carried out in 1994-2007, where each site was occupied at least 3 times. Additionally, data of several continuously recording GPS (CGPS) stations were included in the analysis. GPS data processing was performed with Bernese software package. Site velocities with associated uncertainties were calculated in the stable Eurasian reference frame Active deformation in the coastal belt of the Dinarides is predominately controlled by the counter-clockwise rotation of the Adriatic microplate with respect to Eurasia, around an Euler pole in the Western Alps. The orientation of GPS velocity vectors at coastal sites matches very well the predicted Adria motion trajectories. Orientation of this “Adria Push” ranges from NNW-SSE in the Southern Alps of Slovenia towards the NNE-SSE direction in southern Dalmatia and in the Dinarides of Bosnia and Herzegovina. The rate of shortening across the South-Alpine and Dinaridic fold-thrust belts increases from ∼2 mm/yr in the north to ∼4 mm/yr in the south. In the central and southern Dinarides we detect no statistically significant deformation perpendicular to direction of maximal shortening, which implies extremely low to nonexistent deformation rates on orogen-parallel “Dinaridic” strike-slip faults within the time span of our campaign data. However, a measurable orogen-parallel deformation that could be related to dextral strike-slip activity on geomorphologically prominent NW-SE trending faults is observed north of the Idrija fault in Slovenia and along its southeastern continuation into Croatia. A measurable jump in deformation rates is seen also in the interior of Croatia in the transition zone from the Dinarides into the Pannonian lowlands. In both cases, the currently implied dextral slip rates are in the order of 1 mm/yr.

GPS geodesy; active tectonics; Adriatic microplate; Dinarides

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