Figure 2

P-wave velocity profiles and magnetic data acquired across the Princess Elizabeth Trough (a), off Prydz Bay (b), and south of Sri Lanka (c). All plots: Generic Mapping Tools³⁶. The upper panels display the newly acquired magnetic data along each line, the lower panels the P-wave velocity models. The positions of OBSs, OBHs and land stations are marked by black circles. Lost stations and stations with serious malfunctions are marked by grey circles. Numbers above the stations indicate the OBS/OBH/land station number. Selected magnetic chrons (e.g. M4, M9r) are added to the magnetic data based on identifications from this study. Accordingly, the onset of oceanic crust is marked. Profiles are shown at a common scale. The PET and PB velocity models are aligned at their COBs to highlight the spreading rate differences between them. Details of ray coverage, misfits and uncertainties can be found in the Supplementary Figures S2–S10 and Supplementary Table S11. Further details will be published elsewhere. Abbreviations: COB-continent-ocean boundary (onset of oceanic crust), EANT-East Antarctica, oc-oceanic, PET-Princess Elizabeth Trough, SKP-Southern Kerguelen Plateau.