High resolution global phase velocity distributions

Abstract

We present global phase velocity distributions for fundamental mode Love and Rayleigh waves in the period range 40 to 150 seconds. The models, expressed in terms of spherical harmonic expansions up to degree and order 40, have beed derived from 28,479 Love wave and 33,662 Rayleigh wave measurements. The measurements were made using an automatic procedure based on non‐linear waveform inversion. We show that the results are characterized by lateral resolving radii between 500 and 850 km, a significant reduction from previous work. The improved global resolution is largely due to the inclusion of many more major arc measurements. The power spectra of the models are much whiter than has previously been found. The results show great similarity to the phase velocity distributions derived from the recent a priori model 3‐SMAC, in which the primary relevant features are the crustal thickness and crustal velocity distributions, the cooling oceanic lithosphere and the thick (300km) lithosphere of the continental cratons. The results thus confirm these features. Differences, for example, in the strengths of the crust, ridge and craton signatures should lead to refinement in the thermal and constitutive parameters upon which the a priori model depends.