A comparison of tomographic and geodynamic mantle models

Abstract

[1] Abstract: We conduct a comprehensive and quantitative analysis of similarities and differences between recent seismic tomography models of the Earth's mantle in an attempt to determine a benchmark for geodynamic interpretation. After a spherical harmonic expansion, we find the spectral power and radial correlation of each tomographic model as a function of depth and harmonic degree. We then calculate the correlation, at the same depths and degrees, between all possible pairs of models, to identify stable and model-dependent features (the former being usually of longer spatial wavelength than the latter). We can therefore evaluate the degree of robust structure that seismologists have mapped so far and proceed to calculate ad hoc mean reference models. Tomographic models are furthermore compared with two geodynamic subduction models that are based on plate motion reconstructions. We find systematically low intermediate-wavelength correlation between tomography and convective reconstruction models and suggest that the inadequate treatment of the details of slab advection is responsible. However, we confirm the presence of stable, slab-like fast anomalies in the mid-mantle whose geographic pattern naturally associates them with subduction. This finding, in addition to our analysis of heterogeneity spectra and the absence of strong minima in the radial correlation functions besides the one at $700 km, supports the idea of whole mantle convection with slab penetration through the 660 km phase transition, possibly accompanied by a reorganization of flow.

A method of spherical harmonic analysis in the geosciences via hierarchical Bayesian inference

“…They are produced by calculating the P l values for each iteration of the MCMC chain and finding the means and 95 per cent credible interval bounds. The power spectrum shows the strong degree 1-3 structure in agreement with Becker & Boschi (2002), here reflected in the raw traveltime data. The large amplitudes below Brazil (for PKPab-df) and the south Pacific (for PcP-P), where data coverage is sparse, show that for realistic data sets care must be taken in regions of poor coverage when making inferences based on spherical harmonic expansions; for example our inferences could be weighted by the variance of the computed model at each spatial location.…”

Geophysical and geochemical evidence for cold upper mantle beneath the Equatorial Atlantic Ocean

“…This surface anomaly corresponds to a high-Q body located in the lower part of the upper mantle. Global whole mantle tomographic models (Boschi & Dziewonski, 1999;Ritsema & Van Heijst, 2000;Becker & Boschi, 2002) also show significantly high seismic velocities beneath the Equatorial Mid-Atlantic Ridge (Fig. 11).…”

“…12A) in the Ordovician, about 460 Ma; and 2) prior to closing of the Rheic Ocean (Fig. 12B) (Boschi & Dziewonski, 1999;Ritsema & Van Heijst, 2000) and the average P and S-wave models of Becker & Boschi (2002). The average models enhance common and more stable features of different global tomographic models.…”

The Early Permian Tarim Large Igneous Province: Main characteristics and a plume incubation model

“…More recently, Torsvik et al (2010) used plate reconstructions and tomographic images to show that the edges of the largest heterogeneities in the deepest mantle, possibly stable for 500 Ma, seem to have controlled the eruption of most Phanerozoic kimberlites. Over 80% of all reconstructed kimberlite locations of the past 320 Ma erupted near or over the sub-African plume generation zone defined by large-scale low shear-wave anomalies at the base of the mantle (Becker and Boschi, 2002). Such an association lends strong support to the superplume model of kimberlite formation (Haggerty, 1994) (c) Gibson et al (2006) and investigated the time-space relationship between small-volume, volatile-rich and highly potassic continental melt fractions, such as kimberlites and related rocks, and large-volume continental flood basalts (CFBs).…”