Auxiliary Material for Paper 2004JB003574 A strong lateral shear velocity gradient and anisotropy heterogeneity in the lowermost mantle beneath the southern Pacific

Figure S2 shows the geographic distribution of dT(SKKS-SKS) at CMB entry and exit points, and a general agreement with the trend in the tomography model SAW24B16, though the amplitude of the anomaly is not well matched. It is difficult to quantify the relative contribution to dT(SKKS-SKS) from either the eastern of western borders due to the ambiguity imparted by our limited azimuthal sampling. Two plausible scenarios exist. SKS could arrive earlier due to higher velocities (than tomographically predicted) in the eastern portion of our study area, while SKKS is delayed more than SKS in the western portion of our study area. In this case, the transition from low velocity to average (or high) velocities in the deepest mantle would have to occur over a much smaller scale than depicted in tomography at present, and quite low velocities must persist to the southwest of the lowest velocities in the tomographic predictions, toward the transition to average wavespeeds.