Group velocity of Rayleigh waves in the Antarctic region

Abstract

We analyzed dispersion of intermediate and long period surface waves, recorded at permanent observatories in the Antarctic region, in a tomographic study based on group velocity. We considered Rayleigh waves from available records of all events which occurred during years 1991-1995, with latitude lower than 40°S and magnitude M≥5.0. We performed classic single-station dispersion analysis on the surface wave train to measure group velocity of the Rayleigh fundamental mode in the period range between 30 and 120 s. We iteratively applied two different techniques of filter analysis: a multiple-filter [Dziewonski et al., 1969] and a phase-matched filter algorithm [Herrin, and Goforth, 1977]. We used such dispersion measurements to compute two-dimensional maps of velocity anomalies in the region. We parameterized group velocity with linear splines, and inverted the linear system by means of singular value decomposition. Results are in significant agreement with earlier studies, but reach a considerably higher detail. Our model differentiates well among geologically different regions, such as the old East Antarctica craton, the accreted terranes of West Antarctica, and the oceanic lithosphere surrounded by the ring of mid-ocean ridges. We image slow areas corresponding to hot-spot regions, including a broad anomaly corresponding to recent volcanism in the Ross Sea, where the existence of a mantle plume has been proposed.