Crustal thickness variations in the Aegean region and implications for the extension of continental crust

[1] We installed 5 broadband and 45 short-period temporary seismic stations, distributed partly as a dense, 100-km-long, N-S linear array and partly as a regional network, throughout the Menderes Massif of western Turkey in order to study crust-upper mantle structure and seismicity. In this study, we have combined teleseismic waveform data from these stations with data from several permanent seismic stations to determine crustal thickness variations in the Aegean region. Receiver function studies at seven broadband stations, using the H-κ stacking method, have yielded crustal thicknesses and Vp/Vs ratios over a broad region of the Aegean. A more detailed crustal image was obtained in the central Menderes Massif, where we applied common conversion point stacking to receiver functions obtained from the N-S linear array. The results show a general trend of westward crustal thinning from 36 km in central Anatolia to 28–30 km in the central Menderes Massif to 25 km beneath the Aegean Sea. The results also indicate that crustal thinning in the Aegean is not uniform in the N-S extensional direction. The crust is thinner in the central Menderes Massif (28–30 km of crustal thicknesses) and the Cycladic Massif (25–26 km) than in surrounding regions where crustal thicknesses are 32–34 km. The long-lived elevated Moho under the metamorphic core complexes suggests that the lower crust in the Aegean region is at least 3 times more viscous than that in the Basin and Range Province, where the Moho is much flatter.

[1]  G. Axen,et al.  Field tests of rolling hinges: Existence, mechanical types, and implications for extensional tectonics , 1997 .

[2]  J. Makris,et al.  Crustal structure of the Central Aegean Sea and the islands of Evia and Crete, Greece, obtained by refractional seismic experiments , 1976 .

[3]  Masayuki Kikuchi,et al.  Inversion of complex body waves , 1982 .

[4]  Charles J. Ammon,et al.  Iterative deconvolution and receiver-function estimation , 1999 .

[5]  P. Kendall,et al.  Plumpton-Ferraro Oscillations of a Slowly Rotating Liquid Sphere , 1975 .

[6]  Mark van der Meijde,et al.  Crustal structure beneath broad-band seismic stations in the Mediterranean region , 2003 .

[7]  X. Pichon,et al.  The hellenic arc and trench system: A key to the neotectonic evolution of the eastern mediterranean area , 1979 .

[8]  S. Myers,et al.  Crust and mantle structure across the Basin and Range‐Colorado Plateau boundary at 37°N latitude and implications for Cenozoic extensional mechanism , 1995 .

[9]  D. Cassard,et al.  Multistage exhumation of the Menderes Massif, western Anatolia (Turkey) , 2001 .

[10]  David B. Harris,et al.  Signal-coil calibration of electromagnetic seismometers , 1995 .

[11]  J. Dewey.  Extensional collapse of orogens , 1988 .

[12]  Hiroo Kanamori,et al.  Moho depth variation in southern California from teleseismic receiver functions , 2000 .

[13]  W. Thatcher,et al.  New constraints on the active tectonic deformation of the Aegean , 2004 .

[14]  D. McKenzie.  Active tectonics of the Alpine—Himalayan belt: the Aegean Sea and surrounding regions , 1978 .

[15]  L. Gülen,et al.  Lithospheric Structure of the Marmara and Aegean Regions, Western Turkey , 2002 .

[16]  J. Dewey,et al.  Aegean and surrounding regions: Complex multiplate and continuum tectonics in a convergent zone , 1979 .

[17]  James Jackson,et al.  Active tectonics of the north and central Aegean Sea , 1991 .

[18]  B. Wernicke,et al.  Uniform-sense normal simple shear of the continental lithosphere , 1985 .

[19]  W. R. Buck,et al.  Flexural rotation of normal faults , 1988 .

[20]  B. Wernicke,et al.  On the role of isostasy in the evolution of normal fault systems , 1988 .

[21]  Sobolev,et al.  Seismic Evidence for a Detached Indian Lithospheric Mantle Beneath Tibet. , 1999, Science.

[22]  M. Meijde,et al.  Receiver Function Study of the Hellenic Subduction Zone , 2003 .

[23]  Lupei Zhu.  Deformation in the lower crust and downward extent of the San Andreas Fault as revealed by teleseismic waveforms , 2002 .

[24]  K. Priestley,et al.  Variations in the crustal structure beneath western Turkey , 1998 .

[25]  Lupei Zhu,et al.  Crustal structure across the San Andreas Fault, southern California from teleseismic converted waves , 2000 .

[26]  J. Makris,et al.  Physical properties and state of the crust and upper mantle of the Eastern Mediterranean Sea deduced from geophysical data , 1984 .

[27]  B. Wernicke.  Low-angle normal faults in the Basin and Range Province: nappe tectonics in an extending orogen , 1981, Nature.

[28]  R. O. Hansen,et al.  Study of the crustal thickness and the subducting lithosphere in Greece from gravity data , 1997 .

[29]  T. Reischmann,et al.  Intrusion age of Pan-African augen gneisses in the southern Menderes Massif and the age of cooling after Alpine ductile extensional deformation , 1996, Geological Magazine.

[30]  James Jackson,et al.  The relationship between plate motions and seismic moment tensors, and the rates of active deformation in the Mediterranean and Middle East , 1988 .

[31]  L. Jolivet,et al.  Timing, kinematics and cause of Aegean extension: a scenario based on a comparison with simple analogue experiments , 1999 .

[32]  J. Makris.  Crustal structure of the Aegean Sea and the Hellenides obtained from geophysical surveys , 1975 .

[33]  V. Isik,et al.  The role of the flexural rotation/rolling hinge model in the tectonic evolution of the Alaşehir graben, western Turkey , 2002, Geological Magazine.

[34]  I. Çemen,et al.  Monazite ages and the evolution of the Menderes Massif, western Turkey , 2005 .

[35]  C. Passchier,et al.  An active bivergent rolling-hinge detachment system: Central Menderes metamorphic core complex in western Turkey , 2001 .

[36]  P. Huchon,et al.  The tectonic development of the hellenic arc and the sea of crete: A synthesis , 1982 .

[37]  Demitris Paradissis,et al.  Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus , 2000 .

[38]  W. R. Buck,et al.  Modes of continental lithospheric extension , 1991 .

[39]  I. Çemen,et al.  Structural Evolution of the Tuzgölü Basin in Central Anatolia, Turkey , 1999, The Journal of Geology.

[40]  L. Royden.  Evolution of retreating subduction boundaries formed during continental collision , 1993 .

[41]  J. Spencer.  Role of tectonic denudation in warping and uplift of low-angle normal faults , 1984 .

[42]  J. Brun,et al.  Aegean crustal thickness inferred from gravity inversion. Geodynamical implications , 2004 .

[43]  J. Jackson,et al.  Characteristics and consequences of flow in the lower crust , 2000 .

[44]  P. Gans.  An open‐system, two‐layer crustal stretching model for the Eastern Great Basin , 1987 .

[45]  A. Sheehan,et al.  Mantle discontinuity structure from midpoint stacks of converted P to S waves across the Yellowstone hotspot track , 1997 .

[46]  M. Bohnhoff,et al.  Crustal investigation of the Hellenic subduction zone using wide aperture seismic data , 2001 .