PcP-P travel time residuals plotted at the surface projections of PcP bouncing points. Triangles and circles indicate positive and negative residuals, respectively. The size of the symbol represents the value of the residual, the thickness of symbol lines scales with epicentral distance of the measurement: the thicker the line, the larger the epicentral distance. The largest symbols represent travel-time anomaly of 2.8 seconds (the number of data exceeds 1200).