Until present, seismic surveys have only been carried out offshore and near the coasts of Greenland, where the
crustal structure is affected by oceanic break-up. We present the deep seismic structure of the crust of the interior
of Greenland, based on the new and the only existing so far seismic refraction/wide-angle reflection profile. The
seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the
ice cap in the interior of central-eastern Greenland. The presence of an up to 3.4 km thick ice sheet, permanently
covering most of the land mass, made acquisition of geophysical data logistically complicated. The profile extends
310 km inland in E-W direction from the approximate edge of the stable ice cap near the Scoresby Sund across
the center of the ice cap. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots
along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about
125 kg at 35-85 m depth in individual boreholes.
Given that the data acquisition was affected by the thick ice sheet, we questioned the quality of seismic
records in such experiment setup. We have developed an automatic routine to check the amplitudes and spectra of
the selected seismic phases and to check the differences/challenges in making seismic experiments on ice and the
effects of ice on data interpretation.
Using tomographic inversion and forward ray tracing modelling we have obtained the two-dimensional velocity
model down to a 50 km depth. The model shows a decrease of crustal thickness from 47 km below the centre of
Greenland in the western part of the profile to 40 km in its eastern part. Relatively high lower crustal velocities
(Vp 6.8 – 7.3 km/s) in the western part of the TopoGreenland profile may result from past collision tectonics or,
alternatively, may be related to the speculated passage of the Iceland mantle plume. Comparison of our results
with the new receiver function studies (Kraft et al., personal communication) suggests the possibility for a massive
underplating along the profile.
The origin of the pronounced circum-Atlantic mountain ranges in Norway and eastern Greenland, which have
average elevation above 1500 m with peak elevations of more than 3.5 km near the Scoresby Sund in Eastern
Greenland, is unknown. Our new results on the crustal structure provide constraints for assessment of the isostatic
balance of the crust in Greenland, as well as for examining possible links between crustal composition, rifting
history and present-day topography of the North Atlantic Region.