Thessaly lies on the Aegean (micro-)plate, undergoing internal crustal deformation due to the plate relative motion against the adjacent Anatolian and Nubian plates. As a result, the whole Thessalian Basin was supposed to be under an extensional tectonic regime of N-S direction. However, the recent earthquake sequence of March 2021 which occurred close to the northwestern margin of the basin revealed NE-SW direction of extension. Based on 7-year GPS measurements recorded by stations installed within and around the basin we assessed four deformational parameters for Thessaly aiming at the understanding of the deformation processes that control the region. These parameters are i) the Maximum Horizontal Extension (MAHE), ii) the Total Velocity (TV), iii) the Maximum Shear Strain (MSS), and iv) the Area Strain (AS). The results show that during the monitoring period, Thessaly moved toward the S-SW with a simultaneous clockwise rotation and underwent dispersed deformation mostly associated with dilatation. Focusing on the epicentral area of the 2021 sequence, strain during the 7-year period was rather low in all three strain parameters, implying a mature stage of elastic strain accumulation before the fault rupture., Ilias Lazos, Sotirios Sboras, Konstantinos Chousianitis, Stylianos Bitharis, Evaggelos Mouzakiotis, Vassilios Karastathis, Christos Pikridas, Aristeidis Fotiou and Dimitris Galanakis., and Obsahuje bibliografii
The broader Corinth Gulf region is characterized by a notable active tectonic regime, associated with multiple active fault zones. The continuous N–S extensional tectonics of the area is responsible for the roughly E–W trending active normal fault zones, while individual fault segments are associated with seismic events. Satellite geodesy is a qualitative and quantitative means of estimating the tectonically active setting, based on the recorded motions. The study area is monitored by 14 permanent GPS/GNSS stations, collecting primary geodetic data for a 7-year time period (2008-2014). A 30-sec observation rate was performed, resulting in the extraction of the GPS/GNSS velocity values. The primary geodetic data were processed by applying the triangulation methodology, based on the combination of three different GPS/GNSS stations data, which were considered as the triangle vertices. Triangulation methodology led to the construction of 26 different triangles, while for each of them a series of parameters was determined. In particular, the extracted parameters are: a) Maximum Horizontal Extension, b) Total Velocity, c) Maximum Shear Strain and d) Area Strain. The extracted results are expected to approach, qualitatively and quantitatively, the interpretation of the tectonic regime, as well as to determine new, seismic-related, tectonic features.