Anisotropic tomography of the European lithospheric structure from surface wave studies

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Nita, Blanka, Maurya, Satish, Montagner, Jean-Paul
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: seismology; surface waves; anisotropy; tomography; lithosphere; European continent; [SDU]Sciences of the Universe [physics]; Fennoscandia
• Online Access: https://insu.hal.science/insu-03581659; https://insu.hal.science/insu-03581659/document; https://insu.hal.science/insu-03581659/file/Geochem%20Geophys%20Geosyst%20-%202016%20-%20Nita%20-%20Anisotropic%20tomography%20of%20the%20European%20lithospheric%20structure%20from%20surface%20wave.pdf; https://doi.org/10.1002/2015GC006243

International audience We present continental-scale seismic isotropic and anisotropic imaging of shear wave upper-mantle structure of tectonically diversified terranes creating the European continent. Taking into account the 36-200 s period range of surface waves enables us to model the deep subcontinental structure at different vertical scale-lengths down to 300 km. After very strict quality selection criteria, we have obtained phase wave speeds at different periods for fundamental Rayleigh and Love modes from about 9000 three-component seismograms. Dispersion measurements are performed by using Fourier-domain waveform inversion technique named "roller-coaster-type" algorithm. We used the reference model with a varying average crustal structure for each source-station path. That procedure led to significant improvement of the quality and number of phase wave speed dispersion measurements compared to the common approach of using a reference model with one average crustal structure. Surface wave dispersion data are inverted at depth for retrieving isotropy and anisotropy parameters. The fast axis directions related to azimuthal anisotropy at different depths constitute a rich database for geodynamical interpretations. Shear wave anomalies of the horizontal dimension larger than 200 km are imaged in our models. They correlate with tectonic provinces of varying age-provenance. Different anisotropy patterns are observed along the most distinctive feature on our maps-the bordering zone between the Palaeozoic and Precambrian Europe. We discuss the depth changes of the lithosphere-asthenosphere boundary along the profiles crossing the chosen tectonic units of different origin and age: Fennoscandia, East European Craton, Anatolia, Mediterranean subduction zones. Within the flat and stable cratonic lithosphere, we find traces of the midlithospheric discontinuity.