The electric structure of the schizosphere in SE Thessaly, Greece, and its correlation with active tectonics

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Publiée : Ιαν 1, 2007
DOI : https://doi.org/10.12681/bgsg.16882
A. Tzanis
Department of Geophysics - Geothermy, University of Athens
E. Drosopoulou
Department of Geophysics - Geothermy, University of Athens
Résumé

We report the results of a magnetotelluric study in SE Thessaly, Greece, and their correlation with the active tectonics of the area. The data comprised 14 wide-band (150-0.005 Hz) soundings performed in the periphery of the cities of Volos, Velestino and N. Anghialos. The spatial analysis of the MT impedance tensor shows a transition from a shallow (< 1 km) geoelectric structure associated with apparent local structural features, to the deeper (> 3 km) schizosphere associated with large scale structures with ESE-WNW to SE -NW orientation. Quantitative interpretation was carried out with 2-D inversion and yielded high quality images of the geoelectric structure at depths 3-15 km; this depth range corresponds to the seismogenic layer. Conductive structures in the general E-W direction could be detected and correlated with neotectonic faults. In addition, a possible relic of the now extinct Mikrothivai volcano (1.5±0.1 Ma BCE) has been identified. Within the seismogenic layer the spatial MT data correlate almost exactly with the stress field calculated by inversion of focal mechanisms from local earthquakes and appear to provide an electrical image of the transition from the dextral NE-SW transformation associated with the N. Aegean trench to approximately N-S extension in the study area

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  • Rubrique
  • Geophysics and Seismology
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Références
Bahr, Κ., 1988. Interpretation of the magnetotelluric impedance tensor: regional induction and local telluric distortion, J. Geophys., 62, 119-127.
Caputo, R., and Pavlides, S., 1993. Late Cainozoic geodynamic evolution of Thessaly and surroundings (central - northern Greece), Tectonophysics, 223, 339-362.
Caputo, R., 1990, Geological and Structural Study of the Recent Active and Brittle Deformation of the Neogene - Quaternaty Basins of Thessaly (Central Greece), PhD Thesis, University of Thessaloniki.
Cratchley, CR., 1983. Volos Project, PA 85F. Progress report, IGS component for the period 1st April-30 September 1983, British Geological Survey.
Drakopoulos, J., and Delibasis, N., 1982. The focal mechnanism of earthquakes in the major area of Greece for the period 1947-1981, Univ. of Athens, Seismological Laboratory Publication No 2, 185pp.
Hatzfeld, D., Ziazia, ML, Kementzetzidou, D., Hatzidimitriou, P., Panagiotopoulos, D., Makropoulos, K., Papadimitriou, P., and Deschamps, Α., 1999. Microseismicity and focal mechanisms at the western termination of the north Anatolian Fault and their implications for continental tectonics, Geophys. J. int., 137, 891-908
Kozlovsky, Ye. Α., 1984. The world's deepest well, Scientific American, 251, 106-112.
Kronberg, P., and Guenther, R., 1977. Fracture patterns and principles of crustal fracturing in the Aegean region, Proc. VI Colloquium on the geology of the Aegean region, II, Athens 1977.
Mariolakos, E., and Papanikolaou, D., 1987. Είδος παραμόρφωσης και σχέση παραμόρφωσης -σεισμικότητας στο Ελληνικό Τόξο, Bull. Geol. Soc Greece, XIX, 59-76.
McKenzie, D., and Jackson, J.Α., 1986. A block model of distributed deformation by faulting, J. Geol. Soc. Lon., 143, 349-353.
Michael, A. J., 1984. Determination of stress from slip data: Faults and folds, J. Geophys. Res., 89, 11517-11526.
Michael, A. J., 1987. Use of focal mechanisms to determine stress: A control study, J. Geophys. Res., 92, 357-368.
Papazachos, B.C., Panagiotopoulos, D.G., Tsapanos, T.M., Mountrakis, D.M., and Dimopoulos, G.Ch, 1983. A study of the 1980 summer seismic sequence in Magnesia region of Central Greece, Geophys. J. R. astr. Soc, 75, 155-168.
Polyzos, N., 1977. Untersuchungen zur geologischen Auswertbarkeit von Satelitenaufnahmen am Beispiel Mittelgriechenlands, Thesis, Geolog. Institut, Tech. Univ. Claustahl.
Rodi, W., and Mackie, R.L., 2001. Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion, Geophysics, 66 (1), 174-187.
Scholz, C.H., 1990. The Mechanics of Earthquakes and Faulting, Cambridge University Press. Sims, W.S., Bostick, F.X., Jr., and Smith, H.W., 1971. The estimation of magnetotelluric impedance tensor elements from measured data, Geophysics, 36, 938-942.
Swift, C. M., 1971. Theoretical magnetotelluric and TURAM response from two-dimensional inhomogeneities, Geophysics, 36, 38-52.
Taymaz, T., Jackson, J. Α., and McKenzie, D., 1991. Active tectonics of the north and central Aegean Sea, Geophys. J. Int, 106, 433-490.
Tzanis, Α., and Makropoulos, K., 1999. Magnetotellurics and seismotectonics in the analysis of active domains: An essential Combination? Phys. Chem. Earth (A), 24 (9), 841-847.
Tzanis, Α., Makropoulos, K., Martin, J-L., Cormy, G., and Drakopoulos, I., 1994a. Contribution to the study of tectonic deformation in south-east Thessaly, Greece: Geomagnetic deep sounding and seismotectonic observations. Proceedings, 2nd Congress of the Hellenic Geophys. Union, vol 2, 733-748 Fiorina, Greece, 5-7 May 1993.
Tzanis, Α., Ziazia, M., Kementzetzidou, D., and Makropoulos, K, 1994b. A model of contemporary tectonics in SE Thessaly, Greece, as derived from magnetotelluric, GDS and Seismotectonic investigations. Proceedings, XXIV ESC Gen. Assembly, Athens, Greece, 1994, Vol. 1,419-431.
Yee, E., and Paulson, K.V., 1987. The Canonical decomposition and its relationship to other forms of magnetotelluric impedance tensor analysis, J. Geophys., 61, 173-189.
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