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. 2010 May 8;107(21):9507–9512. doi: 10.1073/pnas.1004856107

Fig. 1.

Fig. 1.

PKiKP-PKIKP travel-time residuals versus epicentral distances for ray paths spanning a turning depth point ranging from 1.72 to 107.14 km (Δ = 121.29°–143.82°). The uncertainty in picking is ± 0.1 s. Differential travel-time residuals have been calculated with respect to the isotropic PREM (3). Blue and red symbols indicate the eastern and the western hemisphere, respectively. Green open symbols refer to the polar data beneath Africa (46). Positive (negative) travel-time residuals show higher (lower) seismic velocity in the top part of the Earth’s IC compared to PREM. The thick solid (dashed) line indicates the predicted PKiKP-PKIKP travel-time residuals by using a PREM-like model 0.5% faster (0.3% slower).