Séminaire le 14 déc 2018 à10h30
Intervenant : Giorgi KHAZARADZE
Professeur agrégé Department of Earth and Ocean Dynamics
Salle Coriolis Observatoire Midi-Pyrénées – 14, avenue Edouard Belin – 31400 Toulouse
I will present a preliminary 3D crustal deformation velocity field of the Iberian Peninsula based on the analysis of more than 400 continuous GPS station data from the last 8 years (2010 to 2018) distributed throughout the Iberian Peninsula, northern Africa and southern France. We describe the procedures followed to obtain a combined uniform velocity solution from daily GPS data using GAMIT/GLOBK software of MIT.
The previous studies have estimated only the 2D horizontal rates, since the vertical component of deformation is more complicated to derive. Only the studies by Serpelloni et al. (2013) and Nguyen et al. (2016) have calculated the vertical rates of deformation in some limited areas of the Iberian peninsula. In the present work, we provide the main results in terms of the velocity vectors in horizontal and up/down directions. The calculated horizontal GPS indicate that the Iberian Peninsula presents a heterogeneous present-day crustal deformation field, which can be grouped into 7 distinct domains/blocks. Each domain is influenced by the geo-tectonic structural configuration of the Iberian Peninsula and by the proximity to the Iberia-Nubia plate boundary. The highest velocities, as well as the highest geodetic strain rates, are detected in the Eastern Betics Shear Zone (EBSZ) and along the Iberia-Nubia plate boundary, areas with the highest seismicity rates. The obtained vertical GPS velocities are preliminary and perhaps, in the future, a more careful treatment of various phenomena affecting the GPS vertical signal (e.g. ocean and tide loading) should be performed in order to better resolve them. However, we do detect points, where the observed vertical rates exceed 10 mm/yr. These motions, although real, obviously cannot be related to the tectonics. For example a subsidence of 6 cm/yr in Guadalentín basin near the city of Lorca is caused by the groundwater extraction. This kind of information is useful for multi-risk analysis since it can provide information of ongoing uplift/subsidence motion, that can be caused by faults, landslides, sediment settlement and/or anthropogenic activities (e.g. groundwater withdrawal, mining).