Localized Ultra‐Low Velocity Zone as a Strong Scatterer at the Core‐Mantle Boundary Beneath Central America

Abstract Small‐scale scatterers in the lower mantle contain key information on the recycling process in the whole mantle. Resolving the fine structures of these scatterers is crucial for understanding the dynamic evolution in the deep Earth. Here, we search for scatterers in the lower mantle beneath Central America and the northwestern Pacific Ocean by events in South America and PKP recordings in Japan. In this work, we perform migration of PKP precursors on the source and receiver sides by raytracing to obtain the distribution map of scatterers, after considering 3D heterogeneous structures. Furthermore, we locate a distinct scatterer at the core‐mantle boundary (CMB) beneath Central America that generates strong PKP precursors with unique slowness and back‐azimuth by array processing, which is compatible with the migration result. Based on waveform modeling, this scatterer is essentially a localized ultra‐low velocity zone (ULVZ) with approximately P‐wave velocity reduction of 6% and a lateral extent of 3°. Heated up of the subducted lithosphere by the core or partial melting of the subducted oceanic crust are plausible sources of the localized ULVZ at the CMB we detect here in the subduction region.