Thickness of the mantle transition zone beneath the South Pacific as inferred from analyses of ScS reverberated and Ps converted waves

We study the thickness of the mantle transition zone beneath the South Pacific in order to determine temperature anomalies associated with presumed hot plumes in the South Pacific Superswell. The ScS reverberation method is used to determine the average thickness between an event-station pair and the Velocity Spectrum Stacking (VSS) method is used to determine the thickness near each station. The thickness obtained by the ScS reverberation method shows that the average thickness beneath the Superswell is less than the globally averaged thickness by 6 km, while the average thickness beneath the Tonga-Fiji subduction is greater than the global average by 10 km. The VSS method shows nearly normal thickness beneath stations used in the Superswell region. We conclude that substantial thinning of the transition zone associated with presumed hot plumes occurs locally beneath the Society hot spot as revealed by our previous SS-precursor study, and is not widespread beneath the whole area of the Superswell.