Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure

Details Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure

Jan 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........15r&link_type=abstract

Ph.D. Thesis Colorado Univ., Boulder.

Mathematics

Logic

Asphericity, Boundaries, Earth Core, Earth Mantle, Earth Planetary Structure, Imaging Techniques, Seismic Waves, Tomography, Multivariate Statistical Analysis, Structural Properties (Geology), Topography, Wave Propagation

Scientific paper

The arrival times of seismic body waves reported to the International Seismological Centre (ISC) were inverted to infer the laterally varying radius of the core-mantle boundary (CMB). The data selection and processing methods are described and evaluated. The ISC global core phase travel time data are very noisy. The geographic distribution of the data is highly nonuniform. We show that for PcP data the coherent signal due to mantle heterogeneity overshadows that arising from the CMB, and that the effects of mantle heterogeneity are mapped into the inferred CMB solutions. Several multivariate statistical techniques were developed to model the residual variance. One such technique was used to infer a correlation length of the spatially averaged data on a two dimensional surface. The PcP data are not correlated across the spatial averaging bins and seem to have a strong bias due to small-scale structure and/or noise. Spatial patterns of CMB models inferred from different phases do not agree. Amplitudes of seismically inferred CMB undulations vary greatly. The sensitivity of inferred CMB models to the processing, spatial averaging procedure, and inversion techniques are investigated. Based on this work, it is concluded that reliable inference of CMB topography is not likely with the current ISC data set or with a spherical harmonic expansion truncated to degree and order six. A synthetic travel time inversion experiment was performed to evaluate the effect of unmodeled 660-km discontinuity topography on the inference of aspherical, volumetric mantle structure. Kernels relating the travel times of seismic body-waves to perturbations in discontinuity radius were derived. The results of these inversions show that significant smearing of the input topographic signal appears in the models of volumetric mantle structure inferred from the synthetic data. Recovery of the input signal improves when solving for higher order radial structure with smooth polynomials or with thinner shells directly below 660 km depth. However, fundamental differences between the kernels for volumetric and topographic structure restrict recovery of the input signal to approximately 80 percent.

Affiliated with

Also associated with

No associations

Rating

Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tomographic imaging of internal Earth structure: The core-mantle boundary and the trade-off between volumetric and topographic structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1264181