%0 Article %J Physics of the Earth and Planetary Interiors %D 2021 %T Imaging paleoslabs and inferring the Clapeyron slope in D`` beneath the northern Pacific based on high-resolution inversion of seismic waveforms for 3-D transversely isotropic structure %A Suzuki, Y. %A Kawai, K. %A Geller, R. J. %P 106751 %K SPECFEM3D GLOBE %X We use waveform inversion to infer high-resolution 3-D models of the S-velocity perturbation δVS and the anisotropy parameter δξ in the lowermost 400Â~km of the mantle beneath the northern Pacific. Our inferred models show three prominent features: (i) a widespread positive δVS layer with Â~100Â~km thickness that exists Â~250Â~km above the core-mantle boundary (CMB), which could be due to a bridgmanite to post-perovskite phase transition related to the D`` discontinuity; (ii) distinct positive -δVS anomalies with positive δξ resolved from 100Â~km to more than 400Â~km above the CMB, which could be the subducted Izanagi, Farallon, and Telkhinia slabs; (iii) a vertically continuous low-δVS anomaly with negative δξ at the edge of the subducted slab, which we interpret as an upwelling plume induced by slab sinking. We infer the Clapeyron slope of the post-perovskite phase transition in the lowermost mantle beneath the northern Pacific to be 10.2Â~ąÂ~1.3Â~MPa/K, based on the δVS gradient as a function of depth for the inferred 3-D VS structure. Our estimated large positive Clapeyron slope at the CMB suggests vigorous convection in the lowermost mantle.