More than 150 events, recently recorded by seven seismic broadband stations (OGS-IAA, IRIS, GSETT3-IDC), have been collected and processed to obtain an overview of the crust and upper mantle shear wave velocities.Group velocities of the fundamental mode Rayleigh and Love waves, in the period range from 15 s to 50 s, are used to obtain tomographic maps of the Scotia Sea region, the tip of Antarctic Peninsula, and the tip of South America. Errors in the measurements, estimated on clusters, are larger for Love waves than for Rayleigh waves and their averages are 0.060 -0.080 km/s and 0.030 -0.040 km/s, respectively.From the regionalisation of the dispersion measurements, we obtain smoothed local dispersion curves in correspondence with the main geological and tectonic features, and from their nonlinear inversion, the shear wave velocity versus depth profiles.The correlation length of the heterogeneity, which can be resolved by Rayleigh waves, varies between 200 and 400 km in most parts of the studied area, but becomes greater near the periphery of the maps. The spatial resolution of Love waves (400 -600 km) is poorer than that of Rayleigh waves, due to the deteriorated path coverage and to the larger errors in the group velocity measurements.Models of the shear wave velocity in the crust and upper mantle for the tip of South America, the Falkland Plateau, the Scotia Sea, the South Sandwich oceanic spreading ridge, the South Sandwich trench, the South Scotia ridge, the tip of Antarctic Peninsula, the Bransfield Strait and the Drake Passage are presented.Our regional models and the existing large-scale models (e.g., CRUST5.1), help to define a 3-D velocity model of the Scotia Sea region to be further investigated by waveform inversion.

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More than 60 events recorded by four recently deployed seismic broadband stations around Scotia Sea, Antarctica, have been collected and processed to obtain a general overview of the crust and upper mantle seismic velocities.Group velocity of the fundamental mode of Rayleigh waves in the period between 10 s to 30 -40 s is used to obtain the S-wave velocity versus depth along ten different paths crossing the Scotia Sea region. Data recorded by two IRIS (Incorporated Research Institutions for Seismology) stations (PMSA, EFI) and the two stations of the OGS-IAA (Osservatorio Geofisico Sperimentale -Instituto Antarctico Argentino) network (ESPZ, USHU) are used.The Frequency-Time Analysis (FTAN) technique is applied to the data set to measure the dispersion properties. A nonlinear inversion procedure, ''Hedgehog,'' is performed to retrieve the S-wave velocity models consistent with the dispersion data.The average Moho depth variation on a section North to South is consistent with the topography, geological observations and Scotia Sea tectonic models.North Scotia Ridge and South Scotia Ridge models are characterised by similar S-wave velocities ranging between 2.0 km/s at the surface to 3.2 km/s to depths of 8 km/s. In the lower crust the S-wave velocity increases slowly to reach a value of 3.8 km/s. The average Moho depth is estimated between 17 km to 20 km and 16 km to 19 km, respectively, for the North Scotia Ridge and South Scotia Ridge, while the Scotia Sea, bounded by the two ridges, has a faster and thinner crust, with an average Moho depth between 9 km and 12 km.On other paths crossing from east to west the southern part of the Scotia plate and the Antarctic plate south of South Scotia Ridge, we observe an average Moho depth between 14 km and 18 km and a very fast upper crust, compared to that of the ridge. The S-wave velocity ranges between 3.0 and 3.6 km/s in the thin (9-13 km) and fast crust of the Drake Passage channel. In contrast the models for the tip of the Antarctic Peninsula consist of two layers with a large velocity gradient (2.3 -3.0 km/s) in the upper crust (6-km thick) and a small velocity gradient (3.0 -4.0) in the lower crust (14-km thick).

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