Abstract

Rayleigh, Love, and PL wave dispersion was investigated for 33 shocks in the Tonga-Kermadec arc and for one shock in the New Hebrides arc. The records were taken at Suva, Fiji with Lamont-I.G.Y. long-period seismographs. All epicenters were relocated using a least squares method programmed for a high-speed digital computer. The shocks were classified into five groups according to region. Each group has similar dispersion characteristics. Lower velocities were found beneath the Lau and South Fiji basins than beneath the Tonga and Fiji ridges. PL waves reflect the same velocity changes found for Rayleigh and Love waves. All the dispersion data are intermediate between typical continental and typical oceanic values. A theoretical calculation for a 21.5 km thick crust with a 7.0 km/sec lower layer was found to fit a path which includes the Lau basin, Fiji ridge, and Fiji basin.

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