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Free keywords:
crustal structure, European Arctic, lithosphere, surface waves, tomography, upper mantle
Abstract:
The goal of this study is to refine knowledge of the structure and tectonic history of the European Arctic using the combination of all available seismological surface wave data, including historical data that were not used before for this purpose. We demonstrate how the improved data coverage leads to better depth and spatial resolution of the seismological model and discovery of intriguing features of upper-mantle structure. To improve the surface wave data set in the European Arctic, we extensively searched for broad-band data from stations in the area from the beginning of the 1970s until 2005. We were able to retrieve surface wave observations from regional data archives in Norway, Finland, Denmark and Russia in addition to data from the data centres of IRIS and GEOFON. Rayleigh and Love wave group velocity measurements between 10 and 150 s period were combined with existing data provided by the University of Colorado at Boulder. This new data set was inverted for maps showing the 2-D group-velocity distribution of Love and Rayleigh waves for specific periods. Using Monte Carlo inversion, we constructed a new 3-D shear velocity model of the crust and upper mantle beneath the European Arctic which provides higher resolution and accuracy than previous models. A new crustal model of the Barents Sea and surrounding areas, published recently by a collaboration between the University of Oslo, NORSAR and the USGS, constrains the 3-D inversion of the surface wave data in the shallow lithosphere. The new 3-D model, BARMOD, reveals substantial variations in shear wave speeds in the upper mantle across the region with a nominal resolution of 1° × 1°. Of particular note are clarified images of the mantle expression of the continent-ocean transition in the Norwegian Sea and a deep, high wave speed lithospheric root beneath the Eastern Barents Sea, which presumably is the remnant of several Palaeozoic collisions.
