[J08-1] Imaging and interpreting lithospheric structures using seismic and geodetic approaches I

[J08-1-04] Coupled anisotropic and isotropic body-wave tomography of the upper mantle beneath northern Fennoscandia - Application of a novel code AniTomo to data from passive seismic experiment LAPNET (Finland)

^○Helena Munzarova¹, Jaroslava Plomerova¹, Eduard Kissling², Ludek Vecsey¹, Vladislav Babuska¹ (1.Institute of Geophysics, Czech Academy of Sciences, Prague, Czech Republic, 2.Institute of Geophysics, Department of Earth Sciences, ETH Zurich, Switzerland)

Seismological investigations of continental mantle lithosphere, particularly of its anisotropic structure, advance our understanding of plate tectonics and formation of continents. Orientation of anisotropic fabrics reflects stress fields during the lithosphere origin and its later deformations. To contribute to studies of large-scale upper-mantle structures, we have developed novel code AniTomo for regional anisotropic tomography. AniTomo allows a simultaneous inversion of relative travel-time residuals of teleseismic P waves both for 3D distribution of isotropic-velocity perturbations and anisotropy in the upper mantle. Weak hexagonal anisotropy with symmetry axes oriented generally in 3D is assumed. The novel code was successfully tested on large series of synthetic datasets and synthetic structures. In this contribution we present results of the first application of AniTomo to data from passive seismic experiment LAPNET (northern Fennoscandia, 2007 - 2009). This Precambrian region is tectonically stable and has a thick anisotropic mantle lithosphere (Plomerova and Babuska, Lithos 2010) without significant thermal heterogeneities. The strongest anisotropy and the largest velocity perturbations concentrate in the mantle-lithospheric part of the tomographic model down to 170km. Regions with laterally and vertically consistent anisotropy can be delimitted there. The anisotropic regions from the tomography correspond to domains of consistent fabric derived from variations of P- and SKS-wave anisotropic parameters (Plomerova et al., SE 2011). Particularly, the western part of the model exhibits a distinct and uniform fabric sharply separated from the surroundings. The eastern boundary of this region gradually shifts westward with increasing depth. We connect the retrieved domain-like anisotropic structure of the mantle lithosphere in the northern Fennoscandia with preserved fossil fabrics of the Archean micro-plates, accreted during the Precambrian orogenic processes.