a, S-velocity model of FWEA18-S4, NECESS-S41 along the profile A shown in the main text. b, The estimated temperature anomaly using a temperature-velocity relationship29 of dVs/T=−3.1×10−4 km s−1K−1. The thick red line shows the estimated temperature at 520 km depth. The thin gray lines show the estimated temperature profiles over a 100 km depth interval around 520 km to accompany the resolution of tomographic studies. c, Estimated topography of wadsleyite-ringwoodite phase transition using a Clapeyron slope of 2 MPa/K23. The purple lines show the estimation, while the thick black line shows the observation. d, Similar as (c), but for a Clapeyron slope of 4 MPa/K23. Note that even though the velocity anomalies in regions A and B are very similar in magnitude, the depths of observed phase X1 have a large difference.