A comparison of cratonic roots through consistent analysis of seismic surface waves

Four cratonic regions are compared using existing dispersion curves and inverting these curves with an identical inversion method and parametrization. The four areas are the Archaean Kaapvaal Craton (southern Africa), Slave Province (central Canada) and Yilgarn Craton (western Australia), and the predominately Proterozoic region of South-Central Finland. The aim of this study is to identify the reliably resolved differences, and similarities, between the four study areas rather than obtaining a 'best' model for each area. Alongside the inversion, we also compare the observed dispersion curves with predicted ones using models with either constant shear velocities or constant composition in the lithosphere. The three main conclusions of this study are that 1) models of constant composition within the lithosphere do not explain the dispersion curves, in fact the less physical ly-based models of constant shear velocity provide a better fit to the data for all of the areas; 2) a low velocity zone in the deep lithosphere or below the lithosphere is resolved beneath the Kaapvaal while the three other areas have no such low velocity zone; 3) in spite of age differences, the shear velocities in the Kaapvaal, Slave and South-Central Finland are similar while the Yilgarn has significantly faster velocities. We also suggest that in order to understand the creation and evolution of the lithosphere a model driven approach to the analysis of surface wave dispersion is a valuable complement to classical inversion of dispersion curves, which suffer from the problem of non-unique solutions. (C) 2008 Elsevier B.V. All rights reserved.