Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

• Published in: Journal of geophysical research. Solid earth 2017-01, Vol.122 (1), p.506-523
• Main Authors: Konstantinou, K. I., Mouslopoulou, V., Liang, W.‐T., Heidbach, O., Oncken, O., Suppe, J.
• Format: Article
• Language: English
• Subjects: Aegean; Algorithms; Axes (reference lines); Crustal stress; Data; Earthquakes; Elasticity; focal mechanisms; Geophysics; Gravitation; Gravity; Greece; Inversions; Lithosphere; Marine; Mathematical models; Orientation; Orientation behavior; Planes; Robustness; Seismic activity; Sensitivity; Solutions; Spreading; Strain; stress inversion; Stresses; Tests
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1002/2016JB013272

In this study we utilize regional and teleseismic earthquake moment tensor solutions in order to infer the contemporary crustal stress in the Greek region. We focus on crustal earthquakes and select only solutions with good waveform fits and well‐resolved nodal planes. A data set of 1614 focal mechanisms is used as input to a regional‐scale damped stress inversion algorithm over a grid whose node spacing is 0.35°. Several resolution and sensitivity tests are performed in order to ascertain the robustness of our results. Our findings show that for most of the Greek region the largest principal stress σ1 is vertically oriented and that the minimum principal stress axis σ3 are subhorizontal with a predominant N‐S orientation. In the SW Peloponnese the orientation of σ3 axes rotates clockwise and in SE Aegean counterclockwise. These results are in agreement with the generally accepted model that slab rollback combined with gravitational spreading of the Aegean lithosphere are the main causes of the extension. Transitions between different faulting types in NW Greece or in the Aegean occur within narrow zones in the order of tens of kilometers. A visual comparison of the principal horizontal stress axes and the principal strain axes derived from GPS observations shows good agreement, suggesting that the crust in the Greek region behaves largely in an elastic manner. Key Points Determination of crustal stress field along a dense grid using 1614 focal mechanisms Minimum stress axes consistent with gravitational spreading of Aegean lithosphere Principal stress and strain axis orientations imply elastic behavior of the crust