PhD defence: Helene A. Kraft

Helene A. Kraft defends her thesis,

Seismic structure of the crust and upper mantle in central-eastern Greenland

Supervisor:
Professor Hans Thybo, IGN

Assessment Committee:
Professor Wolfgang Rabbel, Kiel University - Germany
Associate Professor Bo Holm Jacobsen, Aarhus University
Professor Irina Artemieva (chair), IGN

Summary:
Geophysical and geological knowledge of the interior of Greenland is very limited. The lack of knowledge arises mainly due to the logistical challenges related to conducting geophysical fieldwork on the up to 3.4 km thick ice sheet, which covers around 80% of the land area. This PhD thesis is based on the very first regional passive seismic study in central-eastern Greenland, focusing on the area between Scoresby Sund and Summit. The study aims to image the structure of subsurface Greenland starting from the crust and down to the mantle transition zone. Furthermore, the thesis links these observations with features found at the surface, like the high topography along the east coast and volcanic outcrops.
The core of this study is P to S- and S to P- receiver functions, which image the difference in arrival time between not-converted and converted phases. The receiver functions are jointly inverted for the seismic velocity structure.
The crustal models show a relatively shallow Moho at the east coast (< 20 km), which deepens towards central Greenland (> 50 km). The observed results to not suggest a crustal root as support for the high topography.
Major parts of the mantle transition zone below central-eastern Greenland are substantially thinner than in standard Earth models. Furthermore, the results suggest a low velocity layer within the mantle transition zone.

The thesis is available from the PhD administration office, 04.1.417