A high-resolution map of Hawaiian ULVZ morphology from ScS phases

We use core reflected ScS waves sensitive to a broad region of the core-mantle boundary beneath Hawaii create first high-resolution map Hawaiian ultralow-velocity zone (ULVZ). Positive ScS-S differential times are used identify regions strong slow velocity anomalies in lowermost mantle, and presence pre/post-cursors around main phase confirms sharp top basal ULVZ layer. Pre/post-cursor arrivals mapped into volume across their sensitivity produce detailed image morphology. The variability observed can be interpreted terms varying height or reduction, but large range variations required explain observations suggests that most reflects layer thickness. is large-scale regional feature (∼5-25 km) extending wide area along edge Pacific low-velocity province (LLVP). Variability previous models explained by studies imaging different parts this strongly variable, feature. Maximum thicknesses (no taller than 30 found flat-topped, steep-sided on order 1000 km diameter located west Hawaii. This coincident with previously identified mega-ULVZ, represent root plume, which offset from volcanic surface expression. A tall, asymmetric ridge material east Both maximum heights bounded LLVP south, fast seismic as slab remnants north. points potential geodynamical scenario where dense pushed subducted thicker piles against margins.