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Details
  • Lecturer: Dr. Christian Sue, Université de Franche-Comté (França)
  • Date: Mar, 21, 2018 12:00 am
  • Place: Sala d'Actes de l'Institut de Ciències de la Terra Jaume Almera (ICTJA)
  • Further information: Dra. María Ortuño
Abstract

Recent geodetic analyses in the W-Alps brought new and accurate mapping and quantification of the vertical and horizontal deformations in the belt. Vertical motions appear about 10 times larger than horizontal ones, which support geodynamic models implying isostatic adjustments within the Alp’s orogeny (intrinsic buoyancy forces). This kind of interpretations are also strengthened by the regional correlation observed between the fast uplifting core of the W-Alpine arc, and a strong 200 km deep warm anomaly imaged by the latest tomography. Indeed, still debated deep structures should play a major role in the current dynamics. However, surface processes implying GIA and erosional unloading also play a first role as they directly impact the buoyant equilibrium of the Alps. In the available modelling of such a geodynamic context, uplift should be associated to extensional tectonics. Actually, the alpine seismicity developed all along the arcuate shape of the W-Alps, is characterized by such an extensional faulting associated to a minor component of strike-slip. Thus, there is a quite good qualitative correlation in the overall belt between topography, crustal thickness, extension, and uplift. Nevertheless, looking at the new quantification of the vertical motions, it appears that they are partly uncorrelated with extensional seismicity: the maximum of vertical motion (2,5 mm/yr) is located to the North of the W-Alps, whereas the maximum of extensional seismicity is located more than 150 km southward. On the contrary, horizontal deformations observed by GNSS are very well correlated with the seismicity from a regional viewpoint, both in term of deformation mode and quantification. The talk will point out paradoxal uncorrelations in the Alp’s current tectonism, which resolution should arise from new dynamics’ assessments and from new ongoing projects such as ALPARRAY.

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