Logarithmic scatter plot of RMS velocity amplitude versus period for all EMD modes. Color indicates the distance from the umbral center (marked with an orange symbol in Fig. 1): red points represent data from the umbra, green data from the penumbra, and blue data from the superpenumbra. The four specific locations marked in Fig. 1 are also indicated on the color bar. To improve clarity and reduce sample density, data from every ten adjacent pixels with similar amplitudes and periods are averaged. Some data points in the superpenumbra are partially obscured by those from the penumbra.