The Tararua broadband array, consisting of nine three-component seismometers, was deployed in southern North Island, New Zealand, from February 1991 to September 1992. This L-shaped array had an approximately 40 km N-S arm and 30 km E-W arm. Its primary purpose was to record waveforms from Tonga-Kermadec earthquakes whose propagation paths have spent the majority of their time in the Pacific Plate that has been subducted beneath the Australasian Plate along the Tonga-Kermadec-Hikurangi Margin; the continuous recording allowed simultaneous acquisition of an excellent teleseismic and regional broadband seismogram dataset.For the main experiment, broadband three-component waveforms with P-wave precursive slab phases, up to 15 sec early relative to the Jeffreys-Bullen travel times, have been recorded for 71 events. Multiple frequency analysis of the P waveform shows that the high frequencies (>5 Hz) arrive first, with coherent dispersion below about 4.5 Hz. This behavior can be attributed to a high-velocity layer, 8 to 10-km thick, lying above the cold, fast lithosphere of the subducted Pacific Plate. Polarization analysis of the P-wave precursors show them to arrive at steep incidence angles of 20 degrees to 30 degrees, suggesting the phase refracts off the subducted plate's surface to the array. We observe exceptionally large PL leaking modes from shallow events in the Tonga-Kermadec region to the north.

Anomalies in teleseismic arrivals at stations astride the West African Craton margin in Senegal are large and systematic for rays which have passed beneath the craton margin. Lateral variation in seismic velocity structure beneath the margin persists to several hundred kilometres depth. The major relative delay time and slowness–azimuth anomalies fit a simple model of a steep boundary in the mantle aligned with the major gravity anomaly associated with the craton margin. The mantle beneath the Mauritanide orogenic belt has lower P-velocity than the adjacent craton between ∼80 and 220 km, but higher average velocity both above and below that depth range.