The Experts below are selected from a list of 7689 Experts worldwide ranked by ideXlab platform

Stephan Mueller - One of the best experts on this subject based on the ideXlab platform.

  • structure and dynamics of the eurasian African arabian Plate boundary system objectives tasks and resources of the wegener group
    Journal of Geodynamics, 1998
    Co-Authors: H G Kahle, Stephan Mueller
    Abstract:

    Abstract The Mediterranean-Alpine region marks the broad transition zone between the African/Arabian and Eurasian Plates. In a generalized scheme, the recent major tectonic processes there can be understood as a direct consequence of active sea-floor spreading in the Atlantic Ocean, the Red Sea/Gulf of Aden and NW Indian Ocean spreading centres. The higher spreading rate in the South Atlantic compared to that in the North Atlantic leads to a gradual counterclockwise rotation of the African Plate resulting in a north-northwestward directed push against Eurasia, which in turn leads to a lithospheric shortening of about 5 mm/a increasing to 40 mm/a in active subduction zones. With northwest-southeastward oriented spreading in the North Atlantic the zone of Eurasian/African Plate contact is, therefore, to a large extent under compression thus providing the framework for mountain building processes accompanied by active rifting in preconditioned zones of lithospheric weakness.

  • structure and dynamics of the eurasian African arabian Plate boundary system objectives tasks and resources of the wegener group
    Journal of Geodynamics, 1998
    Co-Authors: Hansgert Kahle, Stephan Mueller
    Abstract:

    Abstract The Mediterranean-Alpine region marks the broad transition zone between the African/Arabian and Eurasian Plates. In a generalized scheme, the recent major tectonic processes there can be understood as a direct consequence of active sea-floor spreading in the Atlantic Ocean, the Red Sea/Gulf of Aden and NW Indian Ocean spreading centres. The higher spreading rate in the South Atlantic compared to that in the North Atlantic leads to a gradual counterclockwise rotation of the African Plate resulting in a north-northwestward directed push against Eurasia, which in turn leads to a lithospheric shortening of about 5 mm/a increasing to 40 mm/a in active subduction zones. With northwest-southeastward oriented spreading in the North Atlantic the zone of Eurasian/African Plate contact is, therefore, to a large extent under compression thus providing the framework for mountain building processes accompanied by active rifting in preconditioned zones of lithospheric weakness.

Jesus Galindozaldivar - One of the best experts on this subject based on the ideXlab platform.

  • plio quaternary paleostresses in the atlantic passive margin of the moroccan meseta influence of the central rif escape tectonics related to eurasian African Plate convergence
    Journal of Geodynamics, 2014
    Co-Authors: Amal Chabli, Ahmed Chalouan, Mostapha Akil, Jesus Galindozaldivar, Patricia Ruano, A C Lopezgarrido, Carlos Sanz De Galdeano, Carlos Marinlechado
    Abstract:

    Abstract The Atlantic Moroccan Meseta margin is affected by far field recent tectonic stresses. The basement belongs to the variscan orogen and was deformed by hercynian folding and metamorphism followed by a post-Permian erosional stage, producing the flat paleorelief of the region. Tabular Mesozoic and Mio-Plio-Quaternary deposits locally cover the Meseta, which has undergone recent uplift, while north of Rabat the subsidence continues in the Gharb basin, constituting the foreland basin of the Rif Cordillera. The Plio-Quaternary sedimentary cover of the Moroccan Meseta, mainly formed by aeolian and marine terraces deposits, is affected by brittle deformations (joints and small-scale faults) that evidence that this region – considered up to date as stable – is affected by the far field stresses. Striated faults are recognized in the oldest Plio-Quaternary deposits and show strike-slip and normal kinematics, while joints affect up to the most recent sediments. Paleostress may be sorted into extensional, only affecting Rabat sector, and three main compressive groups deforming whole the region: (1) ENE–WSW to ESE–WNW compression; (2) NNW–SSE to NE–SW compression and (3) NNE–SSW compression. These stresses can be attributed mainly to the NW–SE oriented Eurasian-African Plate convergence in the western Mediterranean and the escape toward the SW of the Rif Cordillera. Local paleostress deviations may be related to basement fault reactivation. These new results reveal the tectonic instability during Plio-Quaternary of the Moroccan Meseta margin in contrast to the standard passive margins, generally considered stable.

  • ps insar processing methodologies in the detection of field surface deformation study of the granada basin central betic cordilleras southern spain
    Journal of Geodynamics, 2010
    Co-Authors: Joaquim J Sousa, Jesus Galindozaldivar, Antonio M Ruiz, Ramon F Hanssen, L Bastos, Carlos Sanz De Galdeano
    Abstract:

    Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian–African Plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates

  • inversion of moment tensor focal mechanisms for active stresses around the microcontinent iberia tectonic implications
    Tectonics, 2008
    Co-Authors: G De Vicente, Jesus Galindozaldivar, S A P L Cloetingh, A Munozmartin, A Olaiz, Daniel Stich, Ramon Vegas, J Fernandezlozano
    Abstract:

    The Iberian microcontinent and its connected oceanic crust are affected by deformations related to the Eurasian-African Plate boundary. Active stress inversions from populations of moment tensor focal mechanisms have been performed around and inside the Iberian peninsula, using a total of 213 moment tensor estimates. Main results are: 1) The tensorial solutions show better consistency and lower misfits compared to those obtained previously from first P arrival focal mechanisms. 2) Along the Eurasia- Africa western boundary, the type of active stresses progressively changes easternwards from triaxial extension to uniaxial compression along the Terceira Ridge, the Gloria Fault zone and the Gulf of Cadiz. 3) In the Betics-Alboran-Rif zone, uniaxial extension predominates with Shmax N155oE trending. 4) In N Algeria, uniaxial compression reappears. 5) The Iberian foreland is currently under strike-slip to uniaxial extension tensorial conditions.

John Oconnor - One of the best experts on this subject based on the ideXlab platform.

  • age distribution of ocean drill sites across the central walvis ridge indicates Plate boundary control of plume volcanism in the south atlantic
    Earth and Planetary Science Letters, 2015
    Co-Authors: John Oconnor, Wilfried Jokat
    Abstract:

    Abstract The Tristan–Gough hotspot trail on the African Plate consists of the Walvis Ridge and a younger province of seamounts and islands. In order to determine the relative motion between the African Plate and the Tristan–Gough hotspot it is essential to resolve changes in the age and morphology of the Walvis Ridge. A significant problem is, however, to establish how the vigor and flow of hotspot material to the mid-ocean ridge constructed the Walvis Ridge. We have addressed this issue by measuring an 40 Ar/ 39 Ar stratigraphy at three sites across the central Walvis Ridge sampled by Ocean Drilling (DSDP Leg 74). The age–distance relation of volcanism, together with geophysical, geochemical and paleodepth information, suggests collectively that hotspot volcanism was occurring locally c. 72 Ma on an elevated segment of the mid-ocean ridge located close to the Tristan–Gough hotspot. As the mid-ocean ridge migrated away from the hotspot (c. 36 km/Ma) between c. 72 Ma and 68 Ma, hotspot material continued flowing to the mid-ocean ridge and the Walvis Ridge shoaled rapidly (c. 500 m/Ma) to the west, on seafloor that might have been subsiding at a rate consistent with normal crustal cooling. This apparent correlation points to the possibility of an inverse relation between the volume flux of hotspot volcanism and the distance between the mid-ocean ridge and the Tristan–Gough hotspot. We infer that since c. 93 Ma the geometry and motion of the mid-ocean ridge determined where the hotspot material that built the Walvis Ridge was channeled to the Plate surface. Furthermore, interplay between hotspot flow, and the changing geometry of the mid-ocean ridge as it migrated relative to the Tristan–Gough hotspot, might explain the age and morphology of the Walvis Ridge. Our finding provides further evidence that the distribution of hotspot volcanism in the southeast Atlantic expresses interaction between deep mantle (plume) and shallow Plate tectonic and asthenosphere processes.

  • first seamount age evidence for significantly slower African Plate motion since 19 to 30 ma
    Earth and Planetary Science Letters, 1999
    Co-Authors: John Oconnor, P Stoffers, P Van Den Bogaard, Michael Mcwilliams
    Abstract:

    Resolving the time‐space (and compositional) evolution of volcanism along long-lived South Atlantic hotspot trails is important to understanding the connection between hotspot volcanism and mantle plumes. 40 Ar= 39 Ar ages are reported here for rocks dredged from a line of five individual seamounts along an290 km northeast to southwest line extending from the vicinity of Saint Helena Island, and also for Circe Seamount. These seamounts were created in a midPlate setting and could have formed rapidly (1 Myr). The St. Helena Seamount ages reveal a remarkably linear migration rate of volcanism of 20 1m m=yr for at least the past 19 Myr, which is interpreted as the absolute motion of the African Plate. Because this is much slower than estimated for earlier African Plate migration it also represents the first evidence based on seamount ages for a significant deceleration (33%) of the African Plate since at least 19 Ma. However, this change could have occurred as early as 30 Ma when the limited data for the Tristan=Gough hotspot chain are also considered. This deceleration supports a relationship between African Plate speed and the upsurge of hotspot volcanism on the African continent at25 Ma. We suggest that the increased number of oceanic African hotspots between19 and 30 Ma points to a link also between major changes in Plate motion and the onset and continuation of oceanic hotspot volcanism. Our study supports the assumption that chains of individual, rapidly (?) formed seamounts have considerably more potential of providing clear insights into how mantle plumes interact with overriding lithosphere than do those consisting of uninterrupted, more massive lines of hotspot volcanism. © 1999 Elsevier Science B.V. All rights reserved.

Andrea Morelli - One of the best experts on this subject based on the ideXlab platform.

  • subduction and the depth of convection in the mediterranean mantle
    Journal of Geophysical Research, 2003
    Co-Authors: Claudio Faccenna, Laurent Jolivet, Claudia Piromallo, Andrea Morelli
    Abstract:

    [1] We tie together geological data, paleotectonic reconstruction, Plate motion, and tomographic analysis to unravel the history of subduction and back arc extension of the eastern and central Mediterranean. In these two regions, extensional processes started contemporaneously, around 30 Myr ago, but with marked differences. In the eastern region, the Aegean basin opened slowly (∼1 cm/yr) behind a shallow dipping slab (40–45°). The corresponding high-velocity anomaly extends inside the upper mantle and can be also followed in the midmantle down to a depth of at least 1500 km. Its descent into the midmantle initiated most probably during the Late Cretaceous, and the trench moved northeastward, following the path of the Eurasian Plate and under the persistent push of the African Plate. Conversely, in the central Mediterranean region, subduction initiated later, and the motion of the subducting slab is confined to the upper mantle, causing punctuated and rapid episodes of back arc extension (Provencal and Tyrrhenian basins) behind a slab that dips steeply (75°). We explore the causes that control how the slab subducted and interacted with the lower, more viscous part of the mantle.

Tuncay Taymaz - One of the best experts on this subject based on the ideXlab platform.

  • earthquake source parameters along the hellenic subduction zone and numerical simulations of historical tsunamis in the eastern mediterranean
    Tectonophysics, 2012
    Co-Authors: Seda Yolsalcevikbilen, Tuncay Taymaz
    Abstract:

    Abstract We studied source mechanism parameters and slip distributions of earthquakes with M w  ≥ 5.0 occurred during 2000–2008 along the Hellenic subduction zone by using teleseismic P- and SH-waveform inversion methods. In addition, the major and well-known earthquake-induced Eastern Mediterranean tsunamis (e.g., 365, 1222, 1303, 1481, 1494, 1822 and 1948) were numerically simulated and several hypothetical tsunami scenarios were proposed to demonstrate the characteristics of tsunami waves, propagations and effects of coastal topography. The analogy of current Plate boundaries, earthquake source mechanisms, various earthquake moment tensor catalogues and several empirical self-similarity equations, valid for global or local scales, were used to assume conceivable source parameters which constitute the initial and boundary conditions in simulations. Teleseismic inversion results showed that earthquakes along the Hellenic subduction zone can be classified into three major categories: [1] focal mechanisms of the earthquakes exhibiting E–W extension within the overriding Aegean Plate; [2] earthquakes related to the African–Aegean convergence; and [3] focal mechanisms of earthquakes lying within the subducting African Plate. Normal faulting mechanisms with left-lateral strike slip components were observed at the eastern part of the Hellenic subduction zone, and we suggest that they were probably concerned with the overriding Aegean Plate. However, earthquakes involved in the convergence between the Aegean and the Eastern Mediterranean lithospheres indicated thrust faulting mechanisms with strike slip components, and they had shallow focal depths (h