Seismic studies of the crustal structure in West Antarctica 1979–1980—Preliminary results

The Polish Geophysical Expedition to West Antarctica in the summer of 1979–1980 was organized by the Institute of Geophysics of the Polish Academy of Sciences. The purpose of the expedition was to carry out studies of deep structures of the Earth's crust by reflection, refraction and deep seismic sounding methods. Special attention was paid to tectonically active zones and to the contact zones between the blocks of the Earth's crust and the lithospheric plates. Geophysical measurements were carried out in the area extending between 61° and 65°S and between 56° and 66°W. The measurements covered the southern Shetlands, the Antarctic Peninsula, the Bransfield Strait, the Drake Passage, the Palmer Archipelago, the Gerlache Strait and the Bismarck Strait towards the southern Pacific.Deep seismic soundings were made along profiles with a total length of about 2000 km. Seismic reflection measurements were made along profiles about 1100 km long. A detailed analysis of the seismic wave field shows that the structure of the Earth's crust in this part of West Antarctica is very complex. Numerous deep fractures divide the Earth's crust into blocks of different physical properties. The thickness of the Earth's crust changes from 32 km in the region of the South Shetland Islands to 40–45 km in the region of the Antarctic Peninsula. A preliminary geodynamical model of this part of West Antarctica is presented.