The schizosphere-plastosphere boundary through rheological modelling across and along a fold-and-thrust belt: case studies from the Hellenides, Greece, and seismotectonic applications

In this work we used rheological modelling, by means of strength profiles calibration and realization, to determine the depth of the brittle-ductile transition in the Aegean Region, more specifically in relationship with the Hellenides fold and thrust belt. The final aim is to compare the rheological results with the corresponding seismicity and apply the results to seismotectonic issues. Indeed the brittle-ductile transition, though not exactly coinciding with, represents a fair approximation to the seismic-aseismic boundary, which is more precisely related to the velocity weakening-velocity strengthening transition (Tse and Rice 1986; Scholz 1988). During the interseismic period we can, in any case, consider the depth of the brittleductile transition (hereinafter BDT) as a reasonable indicator for the maximum depth extent of (seismogenic) faulting. Accordingly, a precise rheological modelling can help distinguishing the brittle, potentially seismogenic layer, also termed schizosphere (after Scholz 1988), from the undelying, ductilely deforming plastosphere. We then decided to apply the rheological modelling to the Aegean Region for a twofold reason: firstly, it represents one of the most seismically active area all over the world, and therefore it allows to compare and validate the rheological results with a totally independent data source, namely well-located seismicity. Secondly, the Aegean Region is characterized by a dense pattern of seismogenic faults, whose terminations at depths are not always well defined and therefore represent ideal candidates for applying the rheological modelling results, in order to help constraining the geometry and the seismogenic potential of such faults, with the final aim of improving their relative seismotectonic characterization.