A reappraisal of surface wave group velocity tomography in the Subantarctic Scotia Sea and surrounding ridges

A reappraisal of surface wave tomography in the remote Scotia Sea region and surrounding ridges is presented.Newgroup velocity dispersion curveswere obtained from local and regional earthquakes recorded at permanentAntarctic stations from2001 to 2013 and used to update themeasurements reported by Vuan et al. (2000). Rayleighand Love group velocity maps for periods ranging from 15 to 50 s were retrieved using a tomographic inversion.The group velocity anomalies are clearly associated with the major crustal and upper mantle featuresof the Antarctic, Scotia and South American plates. The updated dataset allows for considerable decrease of thecorrelation length of the crustal heterogeneities that can be resolved, especially in the west Scotia Sea, centralScotia Sea and Bransfield Basin. Surface wave tomography resultswere comparedwith CRUST 1.0 group velocitymaps and revealed specific areas where more detailed information is made available by our regional study. Inparticular, low group velocity anomalies of the Bransfield Strait rifting and continental fragments that are detachedfrom the Antarctic Peninsula and spreading along the South Scotia ridge are not shown by the referenceCRUST 1.0 model. A comparison between the average seismic velocities beneath the west and central Scotia Seashows that both have an oceanic-type structure; however, the crust of the central sea is thicker (12–14 km) andslower than that of the 20 Ma old western sea.