Shear wave anisotropy in the upper mantle beneath the Aegean related to internal deformation

Hatzfeld, Denis; Karagianni, Eleni; Kassaras, I.; Kiratzi, Anastasia; Louvari, E.; Lyon‐Caen, H.; Μακρόπουλος, Κ.; Papadimitriou, P.; Bock, G.

doi:10.1029/2001jb000387

Cited by 61 publications

(74 citation statements)

References 53 publications

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“…Şapaş and Boztepe-Güney (2005) have suggested that the crust deforms similarly to the asthenospheric flow direction in this region based on the strain deduced from the GPS displacements (Allmendinger et al 2007). Similar results have been suggested by Hatzfeld et al (2001) for the Aegean area.…”

Section: Resultssupporting

confidence: 76%

“…Also, they have suggested that large surface faults do not have any influence on the upper mantle flow patterns or deformations in the area. In the west of the Isparta Angle, Hatzfeld et al (2001) have investigated the shear wave anisotropy in the upper mantle beneath the Aegean area. They have mapped the fast polarization direction of anisotropy superimposed on the strain deduced from the GPS measurements (McClusky et al 2000).…”

Section: Resultsmentioning

confidence: 99%

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Shear wave splitting in the Isparta angle, southwestern Turkey: Anisotropic complexity in the mantle

Şapaş

Boztepe-Güney

2009

J Earth Syst Sci

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This study presents shear wave splitting analysis results observed at ISP (Isparta) broadband station in the Isparta Angle, southwestern Turkey. We selected 21 good quality seismic events out of nearly 357 earthquakes and calculated splitting parameters (polarization direction of fast wave, φ and delay time between fast and slow waves, δt) from mainly SKS and a few SKKS phases of the selected 21 seismic events. Then, we compared calculated splitting parameters at ISP station (56 • ≤ φ ≤ 205 • ; 0.37 s ≤ δt ≤ 4 s) with those previously calculated at ANTO (Ankara) and ISK (İstanbul) stations (27 • ≤ φ ≤ 59 • ; 0.6 s ≤ δt ≤ 2.4 s and 26 • ≤ φ ≤ 54 • ; 0.6 s ≤ δt ≤ 1.5 s) which are located at 230 and 379 km away from ISP station in central and northwestern Turkey, respectively. The backazimuthal variations of the splitting parameters at ISP station indicate a different and complex mantle polarization anisotropy for the Isparta Angle in southwestern Turkey compared to those obtained for Ankara andİstanbul stations.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Shear wave splitting in the Isparta angle, southwestern Turkey: Anisotropic complexity in the mantle

Şapaş

Boztepe-Güney

2009

J Earth Syst Sci

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“…Coherent energy on the transverse component can be observed at many stations. The crustal anisotropy is, however, obviously different from the mantle anisotropy derived by SKS splitting (Hatzfeld et al 2001). Synthetic receiver functions (Fig.…”

Section: Discussion O F R E S U Lt Smentioning

confidence: 78%

Receiver function study of the Hellenic subduction zone: imaging crustal thickness variations and the oceanic Moho of the descending African lithosphere

Bock

Vafidis

et al. 2003

Geophysical Journal International

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SUMMARY We use data from recently installed broad‐band seismographs on the islands of Crete, Gavdos, Santorini, Naxos and Samos in the Hellenic subduction zone to construct receiver function images of the crust and upper mantle from south of Crete into the Aegean Sea. The stations are equipped with STS‐2 seismometers and they are operated by GFZ Potsdam, University of Chania and ETH Zürich. Teleseismic earthquakes recorded by these stations at epicentral distances between 35° and 95° have been used to calculate receiver functions. The receiver function method is a routinely used tool to detect crustal and upper‐mantle discontinuities beneath a seismic station by isolating the P–S converted waves from the coda of the P wave. Converted P–S energy from the oceanic Moho of the subducted African Plate is clearly observed beneath Gavdos and Crete at a depth ranging from 44 to 69 km. This boundary continues to the north to nearly 100 km depth beneath Santorini island. Because of a lack of data the correlation of this phase is uncertain north of Santorini beneath the Aegean Sea. Moho depths were calculated from primary converted waves and multiply reflected waves between the Moho and the Earth's surface. Beneath southern and eastern Crete the Moho lies between 31 and 34 km depth. Beneath western and northern Crete the Moho is located at 32 and 39 km depth, respectively, and behaves as a reversed crust–mantle velocity contrast, possibly caused by hydration and serpentinization of the forearc mantle peridotite. The Moho beneath Gavdos island located south of Crete in the Libyan Sea is at 26 km depth, indicating that the crust south of the Crete microcontinent is also thinning towards the Mediterranean ridge. This makes it unlikely that part of the crust in Crete consists of accreted sediments transported there during the present‐day subduction process which began approximately 15 Ma because the backstop, i.e. the boundary between the current accretionary wedge of the Mediterranean ridge and the Crete microcontinent, is located approximately 100 km south of Gavdos. A seismic boundary at 32 km depth beneath Santorini island probably marks the crustal base of the Crete microcontinent. A shallower seismic interface beneath Santorini at 20–25 km depth may mark the depth of the detachment between the Crete microcontinent and the overlying Aegean subplate. The Moho in the central and northern Aegean, at Naxos and Samos, is observed at 25 and 28 km depth, respectively. Assuming a stretching factor of 1.2–1.3, crustal thickness in the Aegean was 30–35 km at the inception of the extensional regime in the Middle Miocene.

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“…Only seismic anisotropy (Fig. 10a, Paul et al, 2010;Hatzfeld et al, 2001;Evangelidis et al, 2011) possibly advocates for alongarc mantle flow that could be interpreted as originating from the Kefalonia window, but the not-so-clear nature of alongarc anisotropy (e.g. Russo and Silver, 1994;Long and Silver, 2009;Faccenna and Capitanio, 2013) prevents from being conclusive.…”

Section: Mantle Flowmentioning

confidence: 99%

“…Subduction rates at the North and South Hellenic trenches occur at rates of 5 to 12 mm yr −1 and 25 to 40 mm yr −1 (e.g. McClusky et al, 1s (Paul et al, 2010) 1s (Evangelidis et al, 2011) 1s (Hatzfeld et al, 2001) − o n ti n e n ta l p la te o c e a n ic p la te 2000; Royden and Papanikolaou, 2011;Pérouse et al, 2012), respectively, which offsets the South and North Hellenic subduction zones by a few tenths of kilometres at present day. The formation of the fault itself results from the entry in the subduction zone of a very negatively buoyant oceanic plate to the south, while in the north the subduction of a continental unit of increasingly positive buoyancy proceeds, as the buoyancy difference of the two plate units suffices to trigger a laterally variable regime along the trench .…”

Section: Geological Settingmentioning

confidence: 99%

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

et al. 2013

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Abstract. We designed three-dimensional dynamically selfconsistent laboratory models of subduction to analyse the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigated the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. Two subducting units, which correspond to a negatively buoyant oceanic plate and positively buoyant continental one, are juxtaposed via a trench-perpendicular interface (analogue to a tear fault) that is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr −1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.

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Shear wave anisotropy in the upper mantle beneath the Aegean related to internal deformation

Cited by 61 publications

References 53 publications

Shear wave splitting in the Isparta angle, southwestern Turkey: Anisotropic complexity in the mantle

Shear wave splitting in the Isparta angle, southwestern Turkey: Anisotropic complexity in the mantle

Receiver function study of the Hellenic subduction zone: imaging crustal thickness variations and the oceanic Moho of the descending African lithosphere

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

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