Fig. 4

The sensitivities of displacement Green’s functions to + 1% linear perturbations of TW1. The displacement Green’s functions in the horizontal (left) and vertical (right) components are scaled by 10¹²Rθ in the CE frame. We perturb the bulk modulus (top row), shear modulus (middle row), and density (bottom row) separately in the upper crust at depths of 0–13.88 km, the middle crust at depths of 13.88–24.52 km, the lower crust at depths of 24.52–32.15 km, the LID at depths of 32.15–80 km, the low-velocity zone (LVZ) at depths of 80–220 km, the region above the transition zone at depths of 220–400 km, the transition zone at depths of 400–600 km, the transition zone at depths of 600–670 km, the lower mantle at depths of 670–771 km, the lower mantle at depths of 771–2741 km, and the lower mantle at depths of 2741–2891 km from TW1