GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.2 195 the Mygdonian basin. Along the NNW-SSE transect M W ranges from 7.1-7.2 in the northern sector around Dibra (Albania/FYROM border) to 6.5-6.6. in the western Corinth Gulf region and finally reaching minimum values in the southern Peloponnesus, being equal to 6.4-6.5. Such estimates, as well as the thickness of the seismogenic layer, are fairly consistent with, respectively, the magnitudes of the recent and historical seismicity in the Aegean Region, and its depth distribution, especially when compared with relocated sequences. Concluding remarks . We realized densely spaced 1D strength profiles in order to interpolate them and obtain 2D pseudo-sections representative of the main thermo-rheological properties of the crust ( i.e. maximum shear strength, BDT depth, temperature depth distribution) in the Aegean Region, with special focus on the Hellenides fold-and-thrust belt. We showed that a proper rheological modelling allows to distinguish with sufficient lateral resolution the thickness variations of the brittle, potentially seismogenic layer along 2D transects and that such information can represent an additional and independent (with respect to seismicity data) tool for the improvement of the seismotectonic characterization of the crust, especially as concerns the termination at depth of major structures, whose deep geometries are often uncertain. We also found out that the thickness of the schizosphere varies both across and along the Hellenides belt, thus indicating that rheological variations may occur due to several different factors, such as geothermal gradient, upper crust lithologies, geologic evolution and crustal thicknesses, and all of them must be properly taken into account. Finally, we used the results of the rheological modelling to estimate the maximum expected magnitudes along the two transects and showed that M W max tends to decrease both in a WSW-ENE (from 7.1-7.3 to 6.5-6.6) direction and in the NNW-SSE one (going from 7.1-7.2 to 6.4-6.5); such results are in good agreement with independent data represented by historical seismicity magnitudes and depth distribution, thus confirming the validity of rheological modelling in seismotectonic investigations. References Bos B. and Spiers C.J.; 2002: Frictional-viscous flow of phyllosilicate-bearing fault rock: Microphysical model and implications for crustal strength profiles . J. Geophys. Res . , 107 (B2), doi:10.1029/2001JB000301. Čermák V.; 1982: Crustal temperature and mantle heat flow in Europe . Tectonophys., 83 , 123-142. Cloetingh S.A.P.L., Van Wees J.D., Ziegler P.A., Lenkey L., Beekman F., Tesauro M., Forster A., Norden B., Kaban M., Hardebol N., Bonté D., Genter A., Guillou-Frottier L., Ter Voorde M., Sokoutis D., Willingshofer E., Cornu T. and Worum G.; 2010: Lithosphere tectonics and thermo-mechanical properties: an integrated modelling approach for Enhanced Geothermal Systems exploration in Europe. Earth Science Reviews , 102 (3-4), 159-206. Doutsos T., Koukouvelas I.K. and Xypolias P.; 2006: A new orogenic model for the External Hellenides . In : Robertson A.H.F. and Mountrakis D. (Eds.), Tectonic Development of the Eastern Mediterranean Region. Geol. Soc. London Spec. Publ. , 260 , 507-520. Fytikas M.D. and Kolios N.P.; 1979: Preliminary heat flow map of Greece . In: Cermak V. and Rybach L. (eds), Terrestrial heat flow in Europe . Springer, Berlin, Heidelberg, pp. 197-205. Hurter S. and Haenel R. (Eds.); 2002: Atlas of geothermal resources in Europe . European Commission Office for Official Publications of the European Communities, pp. 93, Luxemburg. Makris J., Papoulia J. and Yegorova T.; 2013: A 3-D density model of Greece constrained by gravity and seismic data . Geophys. J. Int., 194 (1), 1-17. Mountrakis D.; 2006: Tertiary and Quaternary tectonics of Greece . In: Dilek Y. and Pavlides S. (Eds.): Postcollisional tectonics and magmatism in the Mediterranean region and Asia , Geol. Soc. Am. Spec. Paper, 409 , 125-136. Papanikolaou, D.; 2013. Tectonostratigraphic models of the Alpine terranes and subduction history of the Hellenides . Tectonophys, 595 , 1-24. Scholz C.H.; 1988: The brittle-plastic transition and the depth of seismic faulting . Geol. Rundsch., 77 (1), 319-328. Sodoudi F., Kind R., Hatzfeld D., Priestley K., Hanka W., Wylegalla K., Stavrakakis G., Vafidis A., Harjes H.-P. and Bohnhoff M.; 2006: Lithospheric structure of the Aegean obtained from P and S receiver functions. J. Geophys. Res. 111 (B12). Tse S.T. and Rice J.R.; 1986: Crustal earthquake instability in relation to the depth variation of frictional slip properties . J. Geophys. Res., 91 (B9), 9452-9472. Zang S.X., Wei R.Q. and Ning J.Y.; 2007: Effect of brittle fracture on the rheological structure of the lithosphere and its application in the Ordos . Tectonophys., 429 (3-4), 267-285.