HIGH-RESOLUTION GLOBAL PHASE-VELOCITY DISTRIBUTIONS

We present global phase velocity distributions for fundamental mode Lo ve and Rayleigh waves in the period range 40 to 150 seconds. The model s, expressed in terms of spherical harmonic expansions up to degree an d order 40, have beed derived from 28,479 Love wave and 33,662 Rayleig h wave measurements. The measurements were made using an automatic pro cedure based on non-linear waveform inversion. We show that, the resul ts are characterized by lateral resolving radii between 500 and 850 km , a significant reduction from previous work. The improved global reso lution is largely due to the inclusion of many more major are measurem ents. The power spectra of the models are much whiter than ha's previo usly been found. The results show great similarity to the phase veloci ty distributions derived from the recent a priori model S-SMAC, in whi ch 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 conf irm these features. Differences, for example, in the strengths of the crust, ridge and craton signatures should lead to refinement in the th ermal and constitutive parameters upon which the a priori model depend s.