Slab Control on the Northeastern Edge of the Mid-Pacific LLSVP Near Hawaii

Abstract

At the core-mantle boundary, most observed ultralow velocity zones (ULVZs) cluster along the edges of the large low shear velocity provinces (LLSVPs) and provide key information on the composition, dynamics, and evolution of the lower mantle. However, their detailed structure near slab-like structures beneath the mid-Pacific remains particularly challenging because of the lack of station coverage. While most studies of ULVZs concentrate on SKS-complexity, here we report on the multipathing of ScS, which expands the sampling for ULVZs. We find the strongest multipathing along a ULVZ patch located just south of Hawaii and the far northeastern edge of the LLSVP, in a zone ~200 km in width and extending 600 km southward. The anomalous ScS travel times and distorted Sdiff waveforms further reveal patches interrupted by observed enhanced D″ indicative of slab-debris influence on the complexity of the northeastern boundary of the mid-Pacific LLSVP.