Aspherical heterogeneity of the mantle from phase velocities of mantle waves

Abstract

Long-period surface waves are used to map the lateral heterogeneity of the upper 100–600 km of the mantle. There is good correlation of velocity with surface tectonics and heat flow. Convergence regions are generally slow for Love waves and fast for Rayleigh waves. Back arc basins have slower than average shallow mantle. Some island arcs show evidence of fast material at greater depth. Deep-seated slow anomalies underlie the Red Sea–Afar region of north-east Africa, western North American–northern East Pacific Rise, Indian Ocean triple junction and the Tasman Sea–Campbell Plateau regions. The fastest regions are in the north central Australia–New Guinea and the South Atlantic.