Velocity–depth ambiguity and the seismic structure of large igneous provinces: a case study from the Ontong Java Plateau

S U M M A R Y The seismic structure of large igneous provinces provides unique constraints on the nature of their parental mantle, allowing us to investigate past mantle dynamics from present crustal structure. To exploit this crust–mantle connection, however, it is prerequisite to quantify the uncertainty of a crustal velocity model, as it could suffer from considerable velocity–depth ambiguity. In this contribution, a practical strategy is suggested to estimate the model uncertainty by explicitly exploring the degree of velocity–depth ambiguity in the model space. In addition, wide-angle seismic data collected over the Ontong Java Plateau are revisited to provide a worked example of the new approach. My analysis indicates that the crustal structure of this gigantic plateau is difficult to reconcile with the melting of a pyrolitic mantle, pointing to the possibility of large-scale compositional heterogeneity in the convecting mantle.