Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Subduction processes play a major role in plate tectonics and the subsequent geological evolution of Earth. This special issue focuses on ongoing research in subduction dynamics to a large extent (oceanic subduction, continental subduction, obduction…) for both past and active subduction zones and into mountain building processes and the early evolution of orogens. It puts together various approaches combining geophysics (imaging of subduction zones), petrology/geochemistry (metamorphic analysis of HP-UHP rocks, fluid geochemistry and magmatic signal, geochronology), seismology and geodesy (present-day evolution of subduction zones, active tectonics), structural geology (structure and evolution of mountain belts), and numerical modelling to provide a full spectrum of tools that can be used to constrain the nature and evolution of subduction processes and orogeny. Studies presented in this special issue range from the long-term (orogenic cycle) to short-term (seismic cycle).
ISSN: 0264-3707

insu-01287985
https://hal-insu.archives-ouvertes.fr/insu-01287985
https://hal-insu.archives-ouvertes.fr/insu-01287985/document
https://hal-insu.archives-ouvertes.fr/insu-01287985/file/rolland-2016.pdf
DOI : 10.1016/j.jog.2016.03.006

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north–south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E–W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.
ISSN: 0264-3707

hal-01119724
https://hal.archives-ouvertes.fr/hal-01119724
DOI : 10.1016/j.jog.2015.02.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Past studies have shown that high coastal uplift rates are restricted to active areas, especially in a subduction context. The origin of coastal uplift in subduction zones, however, has not yet been globally investigated. Quaternary shorelines correlated to the last interglacial maximum (MIS 5e) were defined as a global tectonic benchmark (Pedoja et al. (2011)). In order to investigate the relationships between the vertical motion and the subduction dynamic parameters, we cross-linked this coastal uplift database with the "geodynamical" databases from Heuret (2005), Conrad and Husson (2009) and Müller et al. (2008). Our statistical study shows that: [1] the most intuitive parameters one can think responsible for coastal uplift (e.g., subduction obliquity, trench motion, oceanic crust age, interplate friction and force, convergence variation, dynamic topography, overriding and subducted plate velocity) are not related with the uplift (and its magnitude); [2] the only intuitive parameter is the distance to the trench which shows in specific areas a decrease from the trench up to a distance of ~300 km; [3] the slab dip (especially the deep slab dip), the position along the trench and the overriding plate tectonic regime are correlated with the coastal uplift, probably reflecting transient changes in subduction parameters. Finally we conclude that the first order parameter explaining coastal uplift is small-scale heterogeneities of the subducting plate, as for instance subducting aseismic ridges. The influence of large-scale geodynamic setting of subduction zones is secondary.
ISSN: 0264-3707

hal-00968538
https://hal.archives-ouvertes.fr/hal-00968538
https://hal.archives-ouvertes.fr/hal-00968538/document
https://hal.archives-ouvertes.fr/hal-00968538/file/henryterraces_v2.pdf
DOI : 10.1016/j.jog.2014.04.001