Structure and Composition of the Australian Continental Mantle

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

van der Hilst EAR-0001136 This project will continue geophysical investigation of the Australian continent, and will provide new constraints on the short (seismic) and long term (flexural) strength of the Australian lithosphere and a better understanding of the origin of the wavespeed variations (composition, temperature, anisotropy) and the dynamic stability of the continent. The work project will expand the previously conducted seismic imaging (with emphasis on anisotropy and uncertainty assessment), develop and apply geodynamical tools to constrain the rheology of the continental upper mantle, and synthesize the results of geophysical probing and the available geological data. Specific objectives are: 1) produce high resolution models for P and S wavespeed and their ratio by joint inversion of P and S travel time residuals and fundamental and higher mode Rayleigh wave dispersion; 2) quantify azimuthal and radial seismic anisotropy by joint interpretation of Rayleigh wave dispersion and body wave birefringence and of the Love-Rayleigh discrepancy; 3) assess model uncertainty by application of different inversion techniques and by using a Spectral Element Method to calculate synthetic seismograms for the 3D anisotropic models; 4) further constrain lithospheric thickness with radial changes in the character of azimuthal and radial anisotropy; 5) determine the (anisotropic) effective elastic thickness of the continental plate and its relationship with seismic lid thickness and anisotropy and with intra-plate deformation; 6) use geodyanmical calculations and seismological constraints to model sub-lithospheric anisotropy and mantle flow around continental keels; 7) combine gravity/geoid anomalies, heat flow, and the 3D wavespeed models to constrain 3D variations of compositional bouyancy in the continental mantle.