Example cross-covariance functions used in Liang et al. (2013). Panels a) and b) are p₁ cross-covariances at (x,y) = (50 Mm,30 Mm) and p₃ cross-covariances at (x,y) = (160 Mm,55 Mm), respectively (see the squares drawn in Fig. 6). In each panel is drawn in a black solid line, and C_n(x,y,t) is shown with a red line and normalized by the maximum of the absolute value of . The dotted lines are the window functions. The amplitudes for the cross-covariance in panel a) are δA = −0.45 and δA_L13 = −0.28, while for panel b) δA = 0.19 and δA_L13 = 0.25.