International audienceWe present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active Aegean region. We focus first on the 130 km long Corinth Rift, an asymmetric graben where a flight of terraces of marine origin are uplifted. We show that the edges of the terraces lie in the footwall of the normal fault bounding the Corinth Rift and correspond to sea-level highstands of late Pleistocene age. Using a detailed analysis of aerial and SPOT imagery supported by field observations, we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault. The elevation of the terraces' inner edges was estimated at 172 sites with an error of + 5 m. This data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level. To date the deformation, we correlate the Corinth terraces with late Pleistocene oxygen-isotope stages of high sea-level stands and with global sea-level fluctuations. Using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary-element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault. We show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000. All the terraces are fitted for fault slip increasing in proportion to terrace age, and the component of regional uplift is found to be less than 0.3 mm yr-'. The best fits give a slip rate of 11 f 3 mm yr-' on the main rift-bounding fault over the last 350 kyr. Other geological and morphologic information allows us to estimate the total age of the main fault (z 1 Ma) and to examine the mechanical evolution of the Corinth Rift. The minimum observed sediment thickness in the Gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6-7 mm yr-' (40 per cent less than estimated with modelling). Even this slip rate is nearly 10 times higher than for comparable features in most of the Aegean and elsewhere in the world. At a larger scale, the spacing and asymmetry of the rift systems in the Aegean suggest strain localization in the upper mantle, with slow extension starting 15 Myr ago or earlier. The more recent (1 Myr), rapid phase of rifting in Corinth partly reactivated this earlier phase of extension. The younger faulting in Corinth appears to result from its present location in the inhomogeneous stress field (process zone) of the south-westward propagating tip of the southern branch of the North Anatolian Fault. We extend these relations to propose a mechanical model for the Late Cenozoic evolution of the Aegean. As the Arabia/Europe collision progressed in eastern Turkey it caused Anatolia to move to the west and the North Anatolian Fault to propagate into the Aegean, where the early slow extension star...
Summary Field studies of active faulting in S Tibet indicate that Quaternary extension has been taking place at a rate of ≃1 cm yr −1 in a direction of ≃ 100°. This implies that underthrusting in the Himalayas now absorbs less than half of the total convergence between rigid India and Asia, the rest being taken up primarily by strike-slip faulting N of the collision belt. En échelon right-lateral, strike-slip faults in S Tibet now allow this corresponding eastward displacement of the plateau with respect to India. The reproducible pattern of faulting obtained from plane-strain indentation experiments on unilaterally confined blocks of plasticine suggests that this extrusion process has occurred during most of the collision history. The Tertiary geological record in SE Asia corroborates a polyphase extrusion model, with displacements in excess of 1000–1500 km, in which India has successively pushed Sundaland, then Tibet and S China towards the ESE. Most of the Middle Tertiary movements may have occurred along the then left-lateral Red River-Ailao Shan Fault Zone, together with the opening of most of the eastern S China Sea. Regional geology, stratigraphy and deformation observed in Yunnan are consistent with this inference, as well as the timing, geometry and rates of sea-floor spreading in the S China Sea. Fast spreading (5 cm yr −1 ) in that sea implies that the Tibetan highlands formed mostly after 17 Ma BP. Sideways movements can also account for the existence of large, conjugate but asymmetric, Tertiary strike-slip faults within Sundaland and the formation of Middle Tertiary pull-apart and rift basins on the Sunda Shelf. Changing directions of opening are predicted in the Mergui and Andaman Basins and the lowlands of Burma, as well as large right-lateral displacements along the Shan Scarp. Most of Sundaland probably lay initially in a frontal position with respect to impinging India and the Shan Plateau may have been a Middle Tertiary analogue of the present Tibetan Plateau. In contrast with dominant overthrusting in the Himalayas, Tertiary strike-slip faulting, with more subordinate folding and thrusting, appears to have been important along and N of the Zangbo Suture. This difference must be accounted for in all models of formation of the Tibet Plateau. The surface of the indentation mark, left by the impaction of India onto the presumably simpler Early Tertiary margin of Asia (> 6 million km 2 ), implies that mountain building and strike-slip faulting have absorbed, perhaps alternately, roughly equal amounts of collisional shortening. Since analogous interplays of extrusion and thickening probably govern the evolution of most collision zones, the Tertiary tectonics of Asia may be the best guide to unravel the interactions between Palaeozoic and Precambrian plates, for which sea-floor spreading constraints are unattainable.
We summarize evidence for Quaternary and active faulting collected in the field during three
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