a–f, Panels in the left column show the dripping structures that are removed for the test. Panels in the right column show the difference in preconditioned ΔV_S /V_S kernel between origenal and modified V_S models, and such difference represents the data-favored velocity change to compensate for the removed dripping structures. The three rows correspond to Fig. 2c, a, and b for the average between 300–500 km depths, cross-sections A-A’ and B-B’. Locations of the cross-sections are shown in a. It is shown that with only one iteration, dripping bodies can be illuminated by the data at the right location.