Waveform Tomography of the Antarctic Plate

The Antarctic continent is a complex assemblage of geological units, ranging from Archean cratons in the east to a Cenozoic assembly of Mesozoic terranes in the west. Present are also the failed Lambert rift system, the inactive West Antarctic rift system and intraplate volcanism in Marie Byrd Land. Covered almost entirely by ice sheets, Antarctica's highly heterogeneous lithospheric structure and its upper mantle are among the least well-studied regions of the Earth’s interior.

The past two decades have seen a significant rise in the number of seasonal and temporary deployments as well as new permanent stations, supplementing and improving the still sparse station coverage in Antarctica. This provided a considerable improvement in both the quantity and quality of seismic data available for the Antarctic continent and its surrounding regions. We assemble a very large dataset of 0.8 million waveform fits, comprising all publicly accessible broadband data in the Southern Hemisphere, with sparser coverage elsewhere, for the best possible sampling of the Antarctic Plate’s crust and the upper mantle.

The new S-wave velocity tomographic model of the crust and upper mantle of Antarctica is computed using the Automated Multimode Inversion (AMI) scheme. AMI first extracts structural information from the surface, S- and multiple S-waves as sets of linearly independent equations. These equations are then combined into a single large linear system that is solved to obtain a tomographic model of the Antarctic crust and upper mantle. We observe the clear delineation of East and West Antarctica by a strong velocity gradient that bisects the continent extending from Coats Land to Victoria Land, following the Transantarctic Mountains. West Antarctica is observed to be underlain by low S-wave velocity anomalies connecting the Antarctic Peninsula, the Amundsen Sea Coast and Marie Byrd Land. The highest S-wave velocity anomalies are observed in central-eastern Antarctica, most of which is underlain by thick, cold cratonic lithosphere. Our tomography maps the boundaries of Antarctica’s cratonic lithosphere and, also, substantial intra-cratonic heterogeneity. It also reveals the patterns of the lithosphere-asthenosphere interactions beneath the cratons and the neighbouring Cenozoic terranes and offers new evidence on the origins of the Transantarctic Mountains and the intraplate volcanism in West Antarctica.