Refinements and Interpretation of Images of the Antarctic Crust and Upper Mantle

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a seismological study of Antarctica. The crust and upper mantle beneath Antarctica remain among the most poorly understood regions directly underlying Earth's surface. Seismic surface wave dispersion is uniquely suited to providing information about the crust and upper mantle beneath Antarctica because surface wave tomography can perform well in regions with relatively few receiving stations and remote seismicity. There are three principal goals for this research: to continue to refine the seismic images of the crust and upper mantle beneath Antarctica and surrounding oceans, to improve methods to quantify the quality of these images, and to begin to elucidate the nature and cause of some of the more prominent seismic velocity anomalies in the uppermost mantle. Prior work was devoted to developing and applying the capabilities to estimate and assess seismic models at high southern latitudes. This research will continue to advance these capabilities, but a larger fraction of the efforts will be devoted to understanding the resulting images of the crust and upper mantle underlying the Antarctic Plate. The work will be divided into the following five subject areas: (1) continued surface wave dispersion measurements and data processing, (2) methodological improvements in surface wave tomography, resolution analysis, and inversion, (3) experiments to determine whether azimuthal anisotropy can be estimated robustly, (4) estimation of a refined model of the crust and upper mantle at high southern latitudes, and (5) development and application of methods to interpret the new model to gain geophysical insight into the temperature, composition, and evolution of the Antarctic asthenosphere, lithosphere, and crust. The rapidly growing seismic data sets from both global networks and temporary arrays in and around Antarctica promise to combine with improvements in surface wave tomography and inversion to significantly refine the images of the seismic structure of the crust and upper mantle beneath the Antarctic Plate. These refinements will help to provide the basis for an improved understanding of the geophysics of the Antarctic lithosphere. Structural and tectonic features that are of particular interest for further elucidation include: the West Antarctic Rift system with implications concerning the separation between East and West Antarctica during the Cenozoic, the East Antarctic craton in relation to other cratons in the world, the SE Indian Ridge with emphasis on the uppermost mantle near the Australian-Antarctic Discordance, the thermal and compositional structure of the upper mantle beneath the Antarctic Plate, and the distribution of anisotropy (radial and azimuthal) across Antarctica and the southern oceans. This research should help to advance broadly our understanding of the Antarctic crust and upper mantle.