Application of BSM to R₁ a), R₂ c), D₁ b), and D₂ d). In each panel, the running difference of the time-distance plot is overlaid with the contour (white dashed line) of the model function Acos(ωt − kx + φ) with the fitted parameters. The fitted parameters are as follows: a) for R₁, P = 180.0 ± 1.8 s, V_p = 47.0 ± 2.6 km s^-1; c) for R₂, P = 178.0 ± 2.0 s, V_p = 49.0 ± 4.5 km s^-1; b) for D₁, P = 180.0 ± 1.0 s, V_p = 47.0 ± 1.4 km s^-1; d) for D₂, P = 178.0 ± 1.0 s,V_p = 49.0 ± 2.8 km s^-1.