Fig. 5

Slowness measurements. (a) The observed differential slownesses, d p ³⁻² (top) and d p ⁴⁻² (bottom). Horizontal axis is slowness (in s/°) as a function of time after the arrival of S2KS (vertical axis). Red, blue, and black stars indicate the predictions from KHOMC, IASP91, and PREM, respectively. (b) RMS misfits of d p ³⁻² and d p ⁴⁻² in s/° for different outer core models. The difference in the misfit between Takana-1 and Tanaka-3 is small. (c) An artificial model of 2D V _s heterogeneity localized near the bottom of the mantle receiver-side structure and the ray paths of S2KS, S3KS, and S4KS, after the Earth-flattening transformation. Dashed and solid blue rays are those for the unperturbed and perturbed Earth models, respectively. Inset shows the entire paths, while the rays near the receiver side CMB are focused below. The V _s anomaly is shown with color scale