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Global seismology

Our tomographic model SEISGLOB2 is shown on this image

The global seismology team in Lyon has broad interests ranging from improving tomographic models of the Earth's mantle and developing new methods for imaging Earth's interior, to understanding the history and evolution of crustal and mantle structures at different scales. We cover different topics of theoretical seismology and data inference. We are particulartly interested in mapping seismic velocities, seismic anisotropy and seismic attenuation, which may provide important constrains on the origin of mantle seismic heterogeneities.

We are interested in the multitude of ways of translating the data extracted from the seismogram into a representation of Earth's structure. Different parts of the seismic record may be used, including body waves, surface waves, normal modes or ambient noise. Different components of the signal can be exploited such as travel-times, amplitudes, deconvolved components, full waveforms or the entire wave-field.



I study the deep Earth interior with the aim of understanding its structure and dynamics. With my colleagues, students and post-doc, I have produced a number of regional and global tomographic models of the shear wave velocity, anisotropy and atten uation of the mantle.

Our latest achievements are a global shear wave velocity model of the entire mantle, SEISGLOB2, which suggests a global change of the shear wave structure near 1000 km depth (Durand et al., 2017) and atomographic model of shear attenuation of the upper mantle QsADR17 (Adenis et al., 2017). Shear wave anisotropy can also be used to map mantle flow and we have recently shown that only plates moving faster than 4 cm/yr can produce sufficient shearing at their base to align anisotropic crystals at the scale of the entire tectonic plates (Debayle et al., 2005; Debayle and Ricard, 2013). Our recent global attenuation models suggest that several thermal plumes of the Pacific oceans are deeply rooted down to
the transition zone and pond in the asthenosphere at the base of tectonic plates (Adenis et al., 2017). Comparison of velocity and attenuation models argue for compositional heterogeneities at the base of cratons and in a number of active regions (Adenis et al., 2017). I'm also interested in mapping seismic discontinuities and we have recently shown the existence of a global low velocity layer located just above the 410 km discontinuity (Tauzin et al., 2010). More detail can be found at with a number of datasets, seismic models and tomographic codes which are made available to the community.

 Benoit TAUZIN (MCF)

My research activity consists in imaging seismically the deep Earth interior, from the lithosphere to the lower mantle, relating observed seismic heterogeneities to what we know about mineral physics, geodynamics and geochemistry. I mainly focus on seismic discontinuities in the transition zone (i.e. 400-700 km depth) and upper mantle (0-400 km). My seismological tools are body-waves reflected (SS-precursors in my PhD) and converted (P-S and S-P receiver functions in Tauzin et al. 2008, 2013) at discontinuities recorded at permanent seismic networks and temporary arrays.

The recent impact of the 15 Feb 2013 meteor in the region of Chelyabinsk, Ural, also provided an interesting exercise of classical seismology. Due to the rarity of such an event (1 per century), its observation provided unusual constraints on the physics of meteoroid collision (Tauzin et al., 2013). I plan to further develop the study of such events on Earth, as they might be interesting analogue experiments for meteor impact surveys on Mars.

 Stéphanie DURAND (CR)