Active Tectonics in the Aegean and surrounding area


Β. Κ. ΠΑΠΑΖΑΧΟΣ
Résumé

The purpose of the present article is to summarize the current scientific knowledge related to the active tectonics of the Aegean and surrounding area (active deformation, lithospheric plate-motions, etc.), as well as describe the main information (data, methods, etc.) which were used to obtain this knowledge. It is pointed out that the understanding of active tectonics has not only theoretical but also practical interest, as it contributes to the solution of problems of direct social impact such as the problem of earthquake prediction. It is shown that most of our present knowledge relies on geophysical, geological and geodetic data. Due to the fact that the Aegean exhibits a variety of geomorphological structures and on going geophysical processes, it has been one of the modern "natural laboratories" where scientists from different parts of the world are working and verify various hypotheses related to our current view of World Tectonics. The Aegean exhibits the typical characteristics of a subduction area, such as the Hellenic Arc (a typical island arc), the Aegean Sea (a marginal sea with typical geomorphological characteristics) and the Collision Zone between the Balkan peninsula and the southwestern Adriatic. A large number of results concerning the Aegean area relies on the use of the spatial distribution of earthquake foci. Accurate data of the last two decades showed that most shallow earthquakes are generated on the shallowest part of the crust (upper 20km) and only along the southern Aegean subduction zone can their depth reach up to 60km. Papazachos and Comninakis (1969/70, 1971) were the first to determine the depth of 109 intermediate-depth events using PcP phases and showed that their foci lied on an amphitheatrically-shaped Benioff zone, which dips from the outer arc (Hellenic Trench) towards the concave part of the Hellenic Arc. This has been confirmed by recent studies, showing that the subduction is separated in a shallower (20-100km), small-dip (-20-30°) section where the lithospheric coupling takes place and events up to M = 8.0 occur, and a deeper (100-180km) part with higher dipping angle (-45°) where events up to M=7.0 occur. Fault plane solutions which have been constructed since the 60s were used for the study of the active tectonics in the Aegean. Their use allowed the detection of reverse faulting along the Hellenic Arc (Papazachos and Delibasis 1969), the Rhodes sinistral fault (Papazachos 1961), as well as the domination of a strong ~N-S extension field throughout the whole back-arc Aegean area (McKenzie 1970, 1972, 1978). The identification of the dextral transform Cephalonia fault (Scordilis et al., 1985) was also of significant importance for the understanding of the Aegean tectonics. This understanding was enhanced by the results obtained about the geophysical lithospheric structure of the Aegean, using either traditional or tomographic methods. These results showed strong crustal thickness variations in agreement with isostasy, detected the presence of a high-velocity subducted slab under the Aegean, with low-velocity/low-Q material in the mantle wedge above the slab, as usually anticipated for a subduction zone. The active deformation of the Aegean has been studied by seismological, geodetic and palaeomagnetic methods. The obtained results allowed the determination of various models describing the active crustal deformation in the Aegean area, showing a anticlockwise motion for Anatolia and a fast southwestern motion of the Aegean microplate at an average rate of ~3.5cm/yr relative to Europe. Similar studies have been performed for the subducted slab. The derivation of such models is further supported by geophysical and geological studies that led to the identification and classification of a large number of active faults, which are related to several strong shallow events in the broader Aegean area. In general, active seismic faults in the Aegean area can be separated in ten main groups, which exhibit different type of faulting. The active deformation and faulting characteristics of the broader Aegean area is the base of the understanding of the driving mechanisms, which control the Aegean active tectonics. In general, the convergence of Africa and Eurasia is responsible for the eastern Mediterranean subduction under the Aegean. The Arabian plate pushes the Anatolia microplate towards the Aegean, thus affecting the active tectonic setting in the Northern Aegean where the dextral motion along the northern Anatolia border continues. Also, the Apulia (Adriatic) anticlockwise rotation results in convergence along the coastal Albania and NW Greece, with trust faulting. However, the main controlling force of the active tectonics in the Aegean is the fast southwest Aegean motion and its overriding of the Mediterranean lithosphère, which is responsible for the large thrust events along the Hellenic Arc, as well as for the large seismicity of the Cephalonia (dextral) and Rhodes (sinistral) faults that are the contact between the Aegean microplate and Apulia and the eastern Mediterranean (east of Rhodes) plates, respectively.

Article Details
  • Rubrique
  • Special and Keynote Lectures
Téléchargements
Les données relatives au téléchargement ne sont pas encore disponibles.
Références
BILLIRIS, Κ., PARADISSIS, D., BEIS, G., ENGLAND, RR, FEATHERSTONE, W., PARSO, Β., CROSS, P., RANDS, P., RAYSON, M., SELLERS, P., ASHKEMAZI, V., DAVISON, M., JACKSON, J. and AMBRASEYS, N. 1991. Geodetic determinations of tectonic deformation in central Greece from 1900 to 1988. "Nature", 350, 124-129.
BARKA, A. A. and KADINSKY-CADE, K. 1988. Strike-slip fault geometry in Turkey and its influence on earthquake activity. "Tectonics", 7, 663 - 684.
BASKOUTAS, J. PANOPOULOS, G, DRAKOPOULOS, J. and MAKROPOULOS, K. 1992. Coda wave analysis using analog data of Athens seismological station. "Bull.Geol. Soc. Greece",28, 201-212.
ΒΟΥΛΓΑΡΗΣ, Ν. 1991. Μελέτη της δομής του φλοιού στη Δυτική Ελλάδα (Ζάκυνθος - ΒΔ Πελοπόννησος). "Διδακτ. Διατριβή, Παν. Αθηνών"
COMNINAKIS, P.E. and PAPAZACHOS, B.C. 1980 Space and time distribution of the intermediate focal depth earthquakes in the Hellenic arc. "Tectonophysics", 70, 35 - 47.
DELIBASIS, N.D. 1982. Seismic wave attenuation in the upper mantle beneath the Aegean. "Pure Appi. Geophys.", 120,820-839.
DELIBASIS, N., MAKRIS, J. and DRAKOPOULOS, J. 1988. Seismic investigation of the crust and the upper mantle in western Greece. "Annal. Geol. Pays Hellen.", 33, 69 - 83.
DENWEY, J.F. 1988. Extensional collapse of Orogens. "Tectonics", 7, 1123 - 1139.
DRAKATOS, G. and DRAKOPOULOS, J. 1991. 3-D velocity structure beneath the crust and upper mantle of the Aegean sea region. "Pure Appi. Geophys.", 135, 401-420.
EKSTROM, G. and ENGLAND, P. 1989. Seismic strain rates in regions of distributed continental deformation. "J. Geophys. Res.", 94, 10231-10257.
HATZFELD, D., PEDOTTI, G., HATZIDIMITRIOU, P., PANAGIOTOPOU-LOS, D., SCORDILIS, M., DRAKOPOULOS, J., MAKROPOULOS, K., DELIBASIS, N., LATOUSAKIS, J., BASKOUTAS, J. and FROGNEUX, M. 1989. The Hellenic subduction beneath the Peloponesse: first results of a microearthquake study. "Earth and Planetary Science Letters", 93, 283-291.
HATZIDIMITRIOU, P.M. 1993. Attenuation of coda waves in northern Greece. "Pure Appi. Geophys." 140, 63- 78.
HODGSON and COCK. 1956. Direction of faulting in Greek earthquakes of August 9-13, 1953. "Pubi. Dom. Obs.", 18, 149-167.
JACKSON, J. and McKENZI, D. 1988. Rates of active deformation in the Aegean Sea and surrounding regions. "Basin Res.", 1, 121-128.
ΚΑΛΟΓΕΡΑΣ, Ι.Σ. 1993. Συμβολή των επιφανειακών σεισμικών κυμάτων στη μελέτη του φλοιού και του πάνω μανδύα στην περιοχή της Ελλάδας. «Διδακτορική Διατριβή, Πανεπιστήμιο Αθηνών», 186 σελ.
KARAKAISIS, G. F. PAPAZACHOS, C.B., SAVAIDIS, A.S. and PAPAZACHOS, B.C. 2001. Accelerating seismic deformation in the north Aegean trough, Greece. "Geophys. J. International" (in press).
KIRATZI, A.A. and PAPAZACHOS, C. B. 1995. Active seismic deformation in the southern Aegean Benioff zone. "J. Geodynamics", 19, 65 - 78.
KIRATZI, A.A., PAPADIMITRIOU, E.E. and PAPAZACHOS, B.C. 1987. A microearthquake survey in the Steno dam site in northwestern Greece. "Annales Geophysicae", 5, 161 - 166.
KISSEL, C. and LAI, C. 1988. The Tertiary geodynamic evolution of the Aegean arc: a palaeomagnetic reconstruction. "Tectonophysics", 146, 183 - 2001.
KONDOPOULOU, D. 2000. Palaeomagnetism in Greece: Cenozoic and Mesozoic components and their geodynamic implications. "Tectonophysics", 326, 131-151.
LEPICHON, X. and ANGELIER, J. 1979. The Hellenic arc and trench sytem: a key to the neotectonic evolution of the eastern Mediterranean area. "Tectonophysics", 60, 1 - 42.
LEPICHON, X., CHAMOT - ROOKE, N., LALEMANT, S., NOOMEN, R. and VEIS, G. 1995. Geodetic determination of the kinematics of central Greece with repsect to Europe: Implictions for eastern Mediterranean tectonics. "J. Geophys. Res.", 100, 1267.5 - 12690.
LIGDAS, C. N., MAIN, I. G. and ADAMS, R.D. 1990. 3 - D structure of the lithosphère in the Aegean Sea region. "Geophys. J. Int.", 102, 219 - 229.
ΛΟΥΒΑΡΗ, E. 2000. Λεπτομερής σεισμοτεκτονική μελε'τη του Αιγαίου και των γειτονικών περιοχών με βάση τους μηχανισμούς γένεσης των μικρών σεισμών. "Διδακτορική Διατριβή, Αριστοτέλειο Πανεπιστήμιου Θεσσαλονίκης", 369 σελ.
MAKRIS, J. 1973. Some geophysical aspects of the evolution of Hellenides. "Bull. Geol. Soc. Greece", 10, 206- 1973.
MAKRIS, J. 1978. The crust and upper mantle of the Aegean region from deep seismic soundings. "Tectonopysics", 46, 269 - 284.
McKENZIE, O.P. 1970. The plate tectonics of the Mediterranean region. "Nature", 226, 239 - 243.
McKENZIE, O.P. 1972. Active tectonics of the Mediterranean region. "Geophys. J. R. astr. Soc", 30, 109 - 185.
McKENZIE, D. P. 1978. Active tectonics of the Alpine - Himalayan belt: the Aegean Sea and surrounding regions. "Geophys. J. R.astr. Soc", 55, 217 - 254.
ORAL, M.B., REILINGER, R.E., TOKSOZ, M. N., KING, R. W., BARKA, A.A., KINIKI, J. and LENK, D. 1995. Global Positioning System offers evidence of plate motions in eastern Mediterranean. EOS, 76, 9-11.
PANAGIOTOPOULOS, D.G. and PAPAZACHOS, B.C. 1985. Travel times of Pn waves in the Aegean and surrounding area. "Geophys. J.R. astr. Soc", 80, 165 - 176.
ΠΑΠΑΖΑΧΟΣ, B.K. 1961. Συμβολή στην ε'ρευνα επί του μηχανισμού γένεσης των σεισμών της Ελλάδας. «Διδακτορική Διατριβή, Πανεπιστήμιο Αθηνών», 75 σελ.
PAPAZACHOS, B.C. 1969. Phase velocities of Rayleigh waves in southeastern Europe and eastern Mediterranean sea. "Pure Appi.Geophys.", 75, 47-55.
PAPAZACHOS, B.C., COMNINAKIS, P. and DRAKOPOULOS, J. 1966. Preliminary results of an investigation of crustal structure in southeastern Europe. "Bull. Seism. Soc. Am.", 56, 1241 - 1268.
PAPAZACHOS, B. C. and DELIBASIS, N.D. 1969. Tectonic stress field and seismic faulting in the area of Greece. "Tectonophysics", 7, 231 - 255.
PAPAZACHOS, B.C. and COMNINAKIS, P.E. 1969/70. Geophysical features of the Greek Island Arc and Eastern Mediterranean Ridge. "Com. Ren. Des Seances de la Conference Reunie a Madrid, Sept. 1969", 16, 74 - 75.
PAPAZACHOS, B.C. and COMNINAKIS, P.E. 1971. Geophysical and tectonic features of the Aegean arc. "J. Geophys. Res.", 76, 8517 - 8533.
PAPAZACHOS, B.C., MOUNDRAKIS, D., PSILOVIKOS, A. and LEVENTAKIS, G. 1979. Surface fault traces and fault plane solutions of May - June 1978 major shocks in the Thessaloniki area. "Tectonophysics", 53, 171-183.
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 the Magnesia region of central Greece. "Geophys. J. R. astr. Soc", 75, 155 - 168.
PAPAZACHOS, B.C., KIRATZI, A.A., HATZIDIMITRIOU, P. and ROCCA, A. 1984. Seismic faults in the Aegean area. "Tectonophysics", 106, 71 - 85.
PAPAZACHOS, B.C. KIRATZI, Α., KARAKOSTAS, B., PANAGIOTOPOULOS, D., SCORDILIS, E. and MOUNTRAKIS, D. 1988. Surface fault traces, fault plane solutions and spatial distribution of the aftershocks of the September 13, 1986 earthquake of Kalamata. "Pure Appi. Geophys.", 126, 55 - 68.
PAPAZACHOS, B.C. KIRATZI, A. and PAPADIMITRIOU, E. 1991. Regional focal mechanisms for earthquakes in the Aegean area. "Pure Appi. Geophys.", 136, 405 - 420.
PAPAZACHOS, B. C, KARAKAISIS, G. F. and HATZIDIMITRIOU, P.M. 1994. Further information on the transform fault of the Ionian sea. "Proc. XXIV Gen. As. Europ. Seism.Com.Athens, 19 - 24 Sept., 1994".
PAPAZACHOS, B.C., PAPADIMITRIOU, E.E., KIRATZI, A.A., PAPAZACHOS, C. B. and LOUVARI, E.K. 1988. Fault plane solutions in the Aegean and surrounding area and their tectonic implication. "Boll. Geof. Teorica Applicata", 39, 199 - 218.
PAPAZACHOS, Β. and PAPAZACHOS, C. 2000. Accelerated preshock deformation of broad regions in the Aegean area. "Pure Appi. Geophys.". 157, 1663-1681.
PAPAZACHOS, B.C., KARAKOSTAS, B.G., PAPAZACHOS, C.B. and SCORDILIS, E.M. 2000a. The geometry of the Wadati - Benioff zone and lithospheric kinematics in the Hellenic arc. "Tectonophysics", 319, 275 -300.
PAPAZACHOS, B.C., KARAKAISI, G.F., PAPAZACHOS, C.B. and SCORDILIS, E.M. 2000b. Earthquake triggering in the north and east Aegean plate boundaries due to the Anatolia westward motion. "Geophys. Res. Letters, 27, 3957 - 3960.
ΠΑΠΑΖΑΧΟΣ Β. Κ., ΜΟΥΝΤΡΑΚΗΣ, Δ. Μ., ΠΑΠΑΖΑΧΟΣ, Κ. Β., ΤΡΑΝΟΣ, Μ. Α., ΚΑΡΑΚΑΪΣΗΣ, Γ. Φ. και ΣΑΒΒΑΙΔΗΣ, Α.Σ. 2001. Τα ρήγματα που προκάλεσαν τους γνωστούς ισχυρούς σεισμούς στην Ελλάδα από τον 5ον αιώνα π.Χ. με'χρι σήμερα "Δεύτερο Πανελλήνιο Συνέδριο Αντισεισμικής Μηχανικής και Τεχνικής Σεισμολογίας, Θεσσαλονίκη 28 - 30 Νοεμβρίου 2001", 1, 17-26.
PAPAZACHOS, C.B. 1992. Anisotropic radiation modeling of macroseismic intensities for estimation of the attenuation structure of the upper crust in Greece. "Pure Appi. Geophys.", 138, 445-469.
ΠΑΠΑΖΑΧΟΣ, K.B. 1994. Δομή του φλοιού και του πάνω μανδύα στη νοτιοανατολική Ευρώπη με αντιστροφή σεισμικών και βαρυτομετρικών δεδομε'νων. "Διδακτορική Διατριβή, Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης", 208 σελ.
PAPAZACHOS, C.B. 1999. Seismological and GPS evindence for the Aegean - Anatolia interaction. "Geophys. Res. Letters", 26, 26453 - 2656.
PAPAZACHOS, C.B., and KIRATZI, A. 1992. A formulation for reliable estimation of active crustal deformation and an application in central Greece. "Geophys. J. Int.", I l l , 424 - 432.
PAPAZACHOS, C.B., HATZIDIMITRIOU, P.M., PANAGIOTOPOULOS, D.G. and TSOKAS G.N. 1995. Tomography of the crust and upper mantle in southeast Europe. "J. Geophys. Res.", 100, 12405 - 12422.
PAPAZACHOS, C.B. and NOLET, G. 1997. Ρ and S deep velocity structure of the Hellenic area obtained by robust nonlinear inersion of travel times. "J. Geophys. Res.", 102, 8349 - 8367.
PAPAZACHOS, B.C. and PAPAZACHOS, B.C. 2001. Precursory seismic deformationin the Aegean area. "Ann. di Geofisica" (in press)
PAYO, G. 1967. Crustal structure of the Mediterranean sea by surface waves, Part I, Group velocity. "Bull. Seism. Soc. Am.", 57, 151 -172.
SCORDILIS, E.M., KARAKAISIS G.F., KARAKOSTAS, B.G., PANAGIOTOPOULOS, D.G., COMNINAKIS, P.E. and PAPAZACHOS, B.C. 1985. Evidence for transform faulting in the Ionian Sea. The Cephalonia island earthquake sequence of 1983. "Pure and Appi. Geophys.", 123, 388 - 397.
SMITH, D.E., KALENIEWICZ, R., ROBBINS, J.W., DUMN, P.J. and TORRENCE, M.H. 1994. Horizontal crustal motion in the central and eastern Mediterranean inferred from satelliete laser ranging measurements. "Geophys. Res. Lett.", 21, 1979 - 1982.
SPERANZA, F., ISLAMI, I., KISSEL, C., HYSENI, A. 1995. Palaeomagnetic evidence for Cenozoic clockwise rotation of the external Albanides. "Earth and Planetary Science Letters", 129, 121 - 134.
SPAKMAN, W. 1986. Subduction beneath Eurasia in connection with the Mesozoic Tethys. "Geol. Mijnb.", 65, 145- 153.
STIROS, S. C. 1993. Kinematics and deformation in central and southwestern Greece from historical triangulation data and implication for the active tectonics of Aegean. "Tectonophysics", 220, 283-300.
STRAUB, Ch., KAHLE, H.G. and SCHIDLER 1997. GPS and geological estimates of the tectonic activity in the Marmara Sea, NW Analolia. "J. Geophys. Res.", 102, 27587 - 27601.
TSELENTIS, G.A. and MAKROPOULOS, C. 1986. Rates of crustal deformation in the gulf of Corinth (central Greece) as determined from seismicity. "Tectonophysics", 124, 55-66.
TSELENTIS, G. Α., DRAKOPOULOS, J. and MAKROPOULOS, C. 1988. On the frequency dependence of Q in the Kalamata (south Greece) region as obtained from the analysis of the coda of the aftershocks of the Kalamata 1986 earthquake. "Tectonophysics", 152, 157 - 159.