3D seismic model of the uppermost crust of the Admiralty Bay area, King George Island, West Antarctica

Majdański, M., Środa, P., Malinowski, M., Czuba, W., Grad, M., Guterch, A., Hegedus, E.

Polish Polar Research

29(4), 2008, 303-318

The understanding of the evolution of Antarctica is one of the main challenges in Earth sciences and the structure of its crust is a key to investigate the tectonic processes. One of the most interesting areas of the West Antarctica is the transition from the oceanic crust of the Pacific Plate to the continental crust of the Antarctic Peninsula through the South Shetland Trench and the volcanic arc of the South Shetland Islands toward the Bransfield Strait rift. In 2007, a 3D seismic survey was performed in the Admiralty Bay (King George Island, South Shetland Islands). It targeted the shallow crustal structure of the volcanic arc. The air-gun shots were recorded using 47 seismic land stations in two deployments. Good quality data allowed for 3D tomographicmodelling of the study area. Sonar measurements datawere used to generate the bathymetry. The first-arrival travel times were inverted for the P-wave velocity models using two different methods: "smooth" seismic tomography with the use of the Iterative Back Projection code (IBP) and tomography with layers (JIVE3D). Obtained velocity anomalies are correlated with the fault structures determined from surface mapping. We were able to trace the Ezcurra Fault down to the depth of 2 km and to recognize the velocities related to the Barton Horst (4.5 km/s) and the Warszawa and Kraków blocks (3.5 km/s). The Mackellar Fault can not be recognized in the deeper part of our model. The estimation of the model uncertainty indicates that the inferred fault structures are resolvable by our data set.