Lithospheric Structure of Greenland and the Northwest Atlantic from Rayleigh Wave Group Velocities
Previously Published Material: Approximately 30-40% of material was presented at the 2013 AGU Fall Meeting.
Abstract ID#: 34160
Most detailed studies of crustal structure have been carried out at the edges of the continent and its margins, using controlled-source experiments. However, the establishment of broadband seismographs across Greenland, principally from the GLATIS and GLISN initiatives, has permitted an increasing number of passive-source studies such as receiver function analysis.
We investigate the crust and uppermost mantle structure of Greenland and the Northwest Atlantic, using Rayleigh wave group velocities from regional earthquakes recorded at the GLATIS and GLISN seismograph stations on Greenland, as well as permanent stations in the eastern Canadian Arctic. Dispersion data for periods from 10 to 80 seconds are combined in a tomographic inversion that solves simultaneously for group-velocity heterogeneity and azimuthal anisotropy. For each grid-point in the group-velocity maps, we extract a 1D dispersion curve, which is inverted for 1D shear-wave velocity structure using a probabilistic modelling scheme. The results are combined to create a pseudo-3D model of the crust and uppermost mantle across the region.
The resulting models indicate crustal thicknesses ranging from ~30 km to almost 50 km beneath mainland Greenland. At shallow depths, the extensive and deep sedimentary basins on the northwest and northeast margins are clearly imaged. Beneath the continental margins and the ocean basin, crustal thickness decreases significantly. In the uppermost mantle, the Greenland mainland region is characterised by high seismic wavespeeds, consistent with a cratonic structure, whereas the Northwest Atlantic shows wavespeeds lower than the global average, likely related to processes at and around the Mid-Atlantic ridge and Iceland hotspot.