Global Positioning System measurements of present day crustal deformation in the Southern Balkans

We integrate continuous and campaign-style GPS data, collected over the last 21 years in the southern Balkans area, which is thought to form a diffuse part of the larger Nubia-Eurasia-Anatolia plate boundary zone. We used the data to estimate crustal velocities at 813 locations relative to the ITRF05-Eurasia fixed reference frame. For all sites, velocity precision is better than 1.5 mm/yr. We use this velocity data set to investigate the implications for active tectonic processes in the Balkan region. The observed velocities in the southern Balkans region are only a few mm/yr relative to stable Eurasia. Nevertheless, the pattern of velocities reveals crustal deformation that can be related to northward motion of the Adria microplate(s), tectonic extrusion of the eastern Alps toward the northeast, and southward motion of the Hellenic trench relative to Eurasia. Our results reveal a previously undocumented pattern of crustal extension in the southern Balkan, some 1100km north of the Hellenic trench in southern Serbia. The velocity data may be interpreted using a model including several rigid crustal blocks separated by actively deforming zones. According to this interpretation, most of Macedonia and part of western Bulgaria appear to move uniformly to the SE, as one crustal block bounded by extension in the southern Serbia and northern Greece. The deformation zone along the western side of this block adjacent to the Dinarides involves some component of strike slip motion. This study helps to refine our understanding of the total breadth of the larger plate boundary zone and also shows that observations coming from GPS networks developed for non-geodetic applications such as surveying engineering and navigation may be useful for tectonics and geodynamics applications requiring very high precision.