Renewal Proposal: Investigation of Global Scale Seismic Mantle and Core Structure Using Forward and Inverse Approaches

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The proposed program of investigation of deep earth structure aims at providing seismological constraints on global geodynamical models of the earth's mantle as well as the core, to help further our understanding of the mechanisms, deep inside the earth, that drive plate tectonics, causing earthquakes and volcanic eruptions. The resulting information on the location, shape and strength of major structures such as upwellings and downwellings will benefit a broader community of non seismologists in geosciences (geodynamicists, mineral physicists and geochemists. This program will directly contribute to the education of 6 graduate students and 2 post-docs. We estimate that it will result in at least 8 publications in refereed journals. This program is aimed at investigating the deep structure of the earth using seismic waveforms collected at global and regional arrays of digital broadband stations using forward and inverse methodology. A central goal is to implement a novel approach based on the combination of accurate seismic wavefield computations in complex three dimensional (3D) structures, as afforded by the efficient C-SEM ("Coupled spectral element method"), for the forward problem, and approximate estimation of Frechet derivatives for the inverse problem. This hybrid approach will allow us to keep the computational costs down while significantly improving resolution through the use of the complete wavefield. We plan, in particular, to: + Develop models of 3D elastic, anelastic and anisotropic structure of the earth's upper mantle using C-SEM + Address the issue of parametrization of large scale tomographic models of the mantle to better constrain the boundaries of major heterogeneous provinces both in the upper and in the lower mantle. + Combine long period waveform and body wave data to map the anisotropic structure of the lithosphere/asthenosphere system at the global scale. + Continue our program of inner core sensitive data collection and interpretation + Investigate further the mechanisms of generation of the earth's low frequency "hum"