Global Rayleigh wave phase-velocity maps from finite-frequency tomography

We report global phase-velocity maps of fundamental-mode Rayleigh waves at periods between 25 and 100 s based on finite-frequency tomography. Rayleigh wave dispersion measurements are made using a multitaper technique for both minor-arc and major-arc wave trains. The global phase-velocity maps confirm many features associated with surface tectonics including the ocean-continent dichotomy and the signature of lithospheric cooling in oceanic plates. In addition, the high-resolution phase-velocity maps reveal a major change in the distribution of small-scale anomalies in the Pacific at different wave periods. We calculate the global average of Rayleigh wave phase velocity in major tectonic regions and show that large discrepancies exist between our model and global crustal and mantle models: (1) In oceanic regions, short-period (