Determination of local active tectonics regime in central and northern Greece, using primary geodetic data

Numerous active fault zones are detected into the central and northern part of Greece, while some of them are associated with destructive seismic events. Geometrically, the fault zone characteristics differentiate, showing both extensional and compressional tectonic features. The geodetic data used, recorded by permanent GPS/GNSS stations, provides a precise analysis the tectonic setting. In particular, 58 permanently installed GPS/GNSS stations are located into the study area, having collected primary data for 7 consecutive year time-period. The calculation of the East and North velocity components and their errors, respectively, derived from each GPS/GNSS station, was carried out implementing the triangulation methodology, based on the combination of three different GPS/GNSS stations each time. The dense GPS/GNSS stations network led to the construction of 1092 different triangles, while the centroid of each triangle was extracted. For each centroid, the following parameters were determined: (1) maximum horizontal extension, (2) minimum horizontal extension, (3) total velocity, (4) maximum shear strain, (5) area strain and (6) rotation. The extracted values were geostatistically processed (interpolation—grid pattern), showing low to medium values, especially north of the extension of the North Aegean Fault System, while the same parameters are high at the southern part of Greece. Therefore, the geological and seismological data are confirmed showing that Central–Northern Greece is tectonically less active than Southern Greece. However, it is mentioned that the neotectonic fault length can be related to the production of significant earthquakes, albeit in longer recurrence intervals.