| Popis: |
Studies of the mean travel-time residual of seismic P-waves propagated from distant sources to stations in Fennoscandia indicate that the mean station residual increases from the centre of the Baltic Shield towards the Atlantic coast. This is interpreted as a decrease of the mean vertical velocity in the upper mantle towards the Atlantic coast. Assuming the usual proportionality between seismic-wave velocity and density, the associated change in the mean upper-mantle density is more than sufficient to support isostatically the height difference between the Scandinavian mountain chain and the lowlands of the central Shield, even assuming an unchanging crustal structure. |
