S-wave velocity structure of the upper mantle beneath the Arctic region from Rayleigh wave dispersion data

Abstract

A new model of the upper mantle structure of the Arctic region based on a representative dataset of Rayleigh wave group velocity dispersion curves from 10 to 250 s period is presented. A surface wave tomography procedure is used to image the group velocity distributions. Local dispersion curves are constructed and inverted to vertical S-wave velocity sections up to the depth of 500 km. Results are presented in two forms: as horizontal slices of S-wave velocity variations relative to the average velocities at several mantle depths and as 2D velocity sections along three profiles crossing different tectonic units. The model shows lateral and vertical velocity variations over the whole depth range within the study area. The most prominent velocity heterogeneities are localized in the uppermost mantle up to the 200 km depth. In this depth range, the velocity anomalies are strongly correlated with the main tectonic structures. The calculated S-wave velocity distribution demonstrates that the upper mantle of the continental shields is characterized by high S-wave velocities and contains regional velocity anomalies associated with small-scale blocks. Low mantle velocities are attributed to the areas with high level of tectonic and seismic activity. Significant difference in deep velocity structure of the marginal seas and deep-water oceanic basins of various ages is revealed. The obtained model suggests some insights into the geodynamical evolution of the lithosphere of the Arctic region.