Lateral Variations in Crustal Structure of Northern Victoria Land From Teleseismic Receiver Functions

We investigate lateral variations in crustal structure of Terra Nova Bay (TNB) area using Receiver Functions (RFs) recorded during four austral summer campaigns (from 1993 to 2000). Seismic stations were deployed around Terra Nova Bay italian base, from the sea to reach the interior of the Transantartic Mountains (TAM), the most striking example of nocontractional mountain belt. RFs was computed from teleseismic waveforms, using frequency-domain deconvolution, following Di Bona's scheme [Di Bona, 1998]. Previous attempts to analyze the data-set, using 1-D models for S-velocity crustal structure, yielded to controversial results, but confirmed the existence of a thinned crust in the area and revealed a deepening of the Moho from the coast to inland [Di Bona et al., 1997]. However, a strong component of converted energy in tangential RFs suggested the presence of dipping and/or anisotropic layers, and stressed the limits of previous technique. To improve our knowledge about Moho geometry in TNB area, we have developed a new RFs inversion scheme. We compute RF components using Frederiksen's method [Frederiksen and Bostock, 2000] for modelling teleseimic wave propagation in anisotropic dipping structures, jointly with a Neighbourhood Algorithm [Sambridge, 1999] which explore the 24-parameters space that characterize our 3-D crustal models. Our main goals are: (1) to test our new RFs inversion methodology; (2) to map Moho-depth and intercrustal S-waves velocity discontinuities in TNB area, with the aim to emphasize dipping and anisotropic layers; (3) to analyze new teleseismic waveforms recorded near TNB base by a seismic station operating in continuous recording, from 1999 to present.