More than 150 events, recently recorded by seven seismic broadband stations
(OGS-IAA, IRIS. GSETT3-IDC), have been collected and processed to obtain a
n overview of the crust and upper mantle shear wave velocities.
Group velocities of the fundamental mode Rayleigh and Love waves, in the pe
riod range from 15 a to 50 s, are used to obtain tomographic maps of the Sc
otia Sea region, the tip of Antarctic Peninsula, and the tip of South Ameri
ca. 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 tec
tonic features, and from their nonlinear inversion, the shear wave velocity
versus depth profiles.
The correlation length of the heterogeneity, which can be resolved by Rayle
igh 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 t
he deteriorated path coverage and to the larger errors in the group velocit
y 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 Passa
ge are presented.
Our regional models and the existing large-scale models (e.g., CRUST5.1), h
elp to define a 3-D velocity model of the Scotia Sea region to be further i
nvestigated by waveform inversion.