Structure of the Greenland Lithosphere and upper Mantle from Receiver Function and Surface Wave Analysis

The GLATIS project (Greenland Lithosphere Analysed Teleseismically on the Ice Sheet) has together with collaborators operated 16 temporary broadband seismographs in Greenland for periods ranging from 3 months to two and a half years. The data has been subjected to both receiver function analysis and to two-station surface wave phase velocity analysis. Data from the permanent broad band seismographs in Greenland are included in the study, as well as data from IRIS station ALE in northern Canada. The receiver function (RF) analysis has produced a model of the depth to Moho over a large portion of Greenland. Some of the lateral variations in the mantle obtained from Rayleigh and Love wave dispersion curves appear to match those found in the crust. We have obtained good quality phase velocities for Rayleigh waves in the period range from 25 to 150 seconds, giving information down to a depth of approximately 250 km. Within this depth range significant velocity differences in the lithosphere structure can be distinguished. Variations in the depth to the mantle discontinuities at approximately 410 km and 660 km have been investigated using the RF method. Both in individual raw RFs for all stations and in migrated depth profiles crossing the continent, the 660 km discontinuity stands out clearly, while the 410 km discontinuity is harder to identify. The data analysis reveals some differences in the travel time delay to the mantle discontinuities along the coasts and across the continent. It is not yet clear if, and by how much, the thickness of the transition zone varies along these profiles and across Greenland. As more data becomes available, we should be able to return with a firmer conclusion.