Detection of Reflected Waves from the Lower Crust on Mizuho Plateau, East Antarctica

Abstract

A reflective lower crust' has been found in some regions of Phanerozoic orogens. In Antarctica it has not been surveyed and is an important target for explosion experiments. Seismic refraction data from the explosion experiments during the 21st Japanese Antarctic Research Expedition (JARE-21) in 1981 were re-analyzed to detect reflected waves from the lower crust. An explosion in Lutzow-Holm Bay with 3000kg of explosive gave well-recorded seismic waves at 27 stations along a 300km profile on the northern Mizuho Plateau, East Antarctica. A band-pass filtered record section with a normal-moveout velocity of 6.3km/s shows clear phases of large amplitudes in a range of 8-16s of two-way travel time; these phases can be considered as wide-angle reflected waves from the lower crust. The reflection depths correspond to about 18-48km. The depth patterns of reflective layers on the Mizuho Plateau can be related to the Bouguer gravity anomalies and are useful for studying the evolution of the Lutzow-Holm Complex.