(a) Fréchet kernels of vertical-component P_diff wave in the source–receiver great-circle plane (top panels) and on the CMB for P-wave speed α. The left panels are kernels of traveltimes and the right panels are kernels of amplitudes. Waves with period of 8 s or longer are included. Both the source and receiver are at the surface and the epicentral distance is Δ= 105°. (b) Fréchet kernels of transverse-component S_diff wave for S-wave speed β. The left panels are kernels of traveltimes and the right panels are kernels of amplitudes. Waves with period of 8 s or longer are included. Both the source and receiver are at the surface and the epicentral distance is Δ= 105°.