Back arcs basins and P‐wave crustal velocity in the Ionian and Aegean regions

Alessandrini, B.; Beranzoli, Laura; Δρακάτος, Γ.; Falcone, C.; Karantonis, G.; Mele, F.; Stavrakakis, G.

doi:10.1029/97gl00082

Cited by 17 publications

(6 citation statements)

References 15 publications

(6 reference statements)

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“…Numerous studies have found low velocities in the upper mantle that are consistent with the Sn efficiency results (e.g. Spakman et al 1993;Alessandrini et al 1997;Piromallo & Morelli 2003). The partial attenuation of Sn in the northern part of the Aegean Sea is related to active extensional deformation in the backarc setting.…”

Section: Seismic Structure Of the Collision Zones In Anatolia And Itssupporting

confidence: 78%

Seismic structure, crustal architecture and tectonic evolution of the Anatolian-African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region

Dilek

Sandvol

2009

104

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The modern Anatolian-African plate boundary is represented by a north-dipping subduction zone that has been part of a broad domain of regional convergence between Eurasia and Afro-Arabia since the latest Mesozoic. A series of collisions between Gondwana-derived ribbon continents and trench-roll-back systems in the Tethyan realm produced nearly East -West-trending, subparallel mountain belts with high elevation and thick orogenic crust in this region. Ophiolite emplacement, terrane stacking, high-P and Barrovian metamorphism, and crustal thickening occurred during the accretion of these microcontinents into the upper plates of Tethyan subduction roll-back systems during the Late Cretaceous-Early Eocene. Continued convergence and oceanic lithospheric subduction within the Tethyan realm were punctuated by slab breakoff events following the microcontinental accretion episodes. Slab breakoff resulted in asthenospheric upwelling and partial melting, which facilitated post-collisional magmatism along and across the suture zones. Resumed subduction and slab roll-back-induced upper plate extension triggered a tectonic collapse of the thermally weakened orogenic crust in Anatolia in the late Oligocene-Miocene. This extensional phase resulted in exhumation of high-P rocks and medium-to lower-crustal material leading to the formation of metamorphic core complexes in the hinterland of the young collision zones. The geochemical character of the attendant magmatism has progressed from initial shoshonitic and high-K calc-alkaline to calc-alkaline and alkaline affinities through time, as more asthenosphere-derived melts found their way to the surface with insignificant degrees of crustal contamination. The occurrence of discrete high-velocity bodies in the mantle beneath Anatolia, as deduced from lithospheric seismic velocity data, supports our Tethyan slab breakoff interpretations. Pn velocity and Sn attenuation tomography models indicate that the uppermost mantle is anomalously hot and thin, consistent with the existence of a shallow asthenosphere beneath the collapsing Anatolian orogenic belts and widespread volcanism in this region. The sharp, north-pointing cusp (Isparta Angle) between the Hellenic and Cyprus trenches along the modern Anatolian-African plate boundary corresponds to a subductiontransform edge propagator (STEP) fault, which is an artifact of a slab tear within the downgoing African lithosphere.

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Section: Seismic Structure Of the Collision Zones In Anatolia And Itssupporting

confidence: 78%

Seismic structure, crustal architecture and tectonic evolution of the Anatolian-African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region

Dilek

Sandvol

2009

104

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“…It seems reasonable to suggest that the reason for that is the Quaternary volcanism of the area (e.g., Kyriakopoulos et al, 1990;Papazachos and Panagiotopoulos, 1993;Morris, 2000), which has weakened the Attica crust. A soft crust for Attica relative to Viotia has also been inferred by Alessandrini et al (1997) due to the existence of a low-velocity zone of P-waves. Although the last 300 years may represent a small fraction of recurrence intervals of large earthquakes, we note that no large events have been reported for the West Attica region as opposed to four eventsN6.0 Ms in Viotia (1853-1893-1914-1938Fig.…”

Section: Fault Segmentation Pattern At the End Of The Gulf Of Corinthmentioning

confidence: 94%

DEM-based morphometry of range-front escarpments in Attica, central Greece, and its relation to fault slip rates

2005

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“…Seismic velocities in the Aegean have been imaged in traveltime tomography studies, ranging from ones at large or global scale, sampling down to 1400 km depth or deeper (Spakman et al 1993; Bijwaard et al 1998; Kárason & van der Hilst 2000; Schmid et al 2006), via studies of the upper mantle of the whole Euro‐Mediterranean (Piromallo & Morelli 1997; Marone et al 2004) or the Ionian‐Aegean region (Alessandrini et al 1997a,b), to very local imaging of the crust around the KTF (Sachpazi et al 2000) and the Corinth and Evvia rifts (Tiberi et al 2000). An observation of special relevance from global tomography is the extent of the slab anomaly down to at least 1200 km depth, that is, much deeper than can be inferred from the active Wadati‐Benioff zone.…”

Section: Introductionmentioning

confidence: 99%

Svelocity structure and radial anisotropy in the Aegean region from surface wave dispersion

Endrun¹,

Meier²,

Lebedev³

et al. 2008

Geophysical Journal International

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SUMMARY The lithospheric structure of the Aegean region is investigated by analysis of Rayleigh‐wave fundamental mode dispersion measurements. Isotropic 1‐D models for almost 100 two‐station ray paths across the region display distinct variations in the Moho depth and crustal S‐wave velocities. The descending slab of the subducting African plate can be resolved down to 120 km depth beneath the volcanic arc. Three different regions are distinguished in terms of Moho depth: (1) The forearc, with large crustal thicknesses between 38 and 48 km and an average of 43 km, (2) the northern Aegean, with an average Moho depth of 28 km and (3) the southern Aegean (central volcanic arc, i.e. Cyclades, and Sea of Crete) with an even thinner crust of around 25 km. Lateral variations in structure between 25 and 55 km depth indicate a marked difference between the western and eastern forearc, collocated with pronounced changes in trench and slab geometry as well as published deformation rates. S velocities between 25 and 55 km depth are low everywhere beneath the forearc but increase from the Peleponnesus to Crete. An abrupt change occurs between western and central Crete in terms of the visibility of the Aegean Moho and the seismic structure of the lithospheric mantle wedge: An Aegean mantle wedge with S velocities above 4.4 km s−1 is only observed to the east of central Crete, whereas to the west velocities of less than 4.0 km s−1 occur down to the plate contact. These low velocities above the slab may indicate the presence of a melange of metamorphic rocks at the depths. A low‐velocity asthenospheric layer is observed beneath the Sea of Crete and the Cyclades below 40 km depth, between the thinned lithosphere above and the slab below. The observed radial anisotropy in the northern part of the Aegean is likely to be due to preferred orientation of anisotropic minerals within the lower crust, possibly caused by lateral ductile flow associated with recent lithospheric extension.

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Back arcs basins and P‐wave crustal velocity in the Ionian and Aegean regions

Cited by 17 publications

References 15 publications

Seismic structure, crustal architecture and tectonic evolution of the Anatolian-African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region

Seismic structure, crustal architecture and tectonic evolution of the Anatolian-African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region

DEM-based morphometry of range-front escarpments in Attica, central Greece, and its relation to fault slip rates

Svelocity structure and radial anisotropy in the Aegean region from surface wave dispersion

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