CRUSTAL PROPERTIES ACROSS THE TRANSITION FROM OROGENIC TO CRATONIC AREA FROM SEISMOLOGICAL ANALYSIS

The mechanism of support for the present topography of Scandinavia is not well explained by current crustal models. High topography in Norway and Sweden (Scandinavian Alps) is directly in contact with a relatively flat region (the Baltic shield). A crustal root beneath the Scandinavian Alps, expected from Airy isostatic calculation, is not present and the gravity anomaly map suggests lateral variations in density to support present day topography. To bring new constrains on the variation of crustal properties we use P receiver functions and ambient seismic noise. Our new crustal thickness map show a relatively thickening of the crust from the Atlantic coast to the Gulf of Bothnia without correlation with the surface topography. We identify also the presence of a high velocity layer at the base of the crust beneath the shield and the presence of a low velocity layer in the upper middle crust beneath the orogen. We will discuss about interpretation of these results in terms of potential mechanism to explain the present day topography in this region.