Fig. 2.

Estimation of GpV and PhV from the displacement field u(z, x, t) for the third push, i.e., n = 3. (a) The displacement field was averaged along the z-axis to calculate the displacement image I(x, t). Black lines were estimated using Hough transform and their slopes represent GpV. (b) Phase values at four different frequencies. After Fourier transformation of displacement images, phase data were extracted and unwrapped from the frequency image I(x, ω). (c) Estimated PhVs using phase data from subfigure (b).