Fig. 18From: Estimation of phase velocity using array observation of microtremors with arbitrary shapeFourier amplitudes of observed microtremors at the site (solid colored lines) and noise floor of the sensor (solid gray line). The observed data have sufficient SNR in the frequency range of 4 to 16 Hz. Note that the SNR is shown as the power ratios which are calculated as colored lines divided by a gray line in the panel aBack to article page