2.3.2. Correlation Analyses

As the selected recording period was free of major anomalous ocean activities (e.g., ocean storm, typhoon, hurricane) in Atlantic or Pacific Oceans (according to National Hurricane Center, NHC), the DF microseisms were generated by the interactions of the incoming ocean waves and those reflected at the continental margin. In order to investigate the significance of the continental slope in the excitation of the DF microseisms quantitatively under normal sea states, correlation analyses of time histories between DF microseisms and ocean wave energy were carried out by considering the time-dependent variation of frequency composition and energy levels. A few DF microseism events were identified as their PSD levels are higher than the average PSDs in the whole recording period in the frequency band. Their generation mechanisms were explored by comparing temporal and spatial variations of the PSDs to the migration patterns of ocean wave fronts in WWIII hindcasts in corresponding frequency bands, as well as comparing the frequency band of each event to the DWF of ocean buoys in four groups. For the entire period of microseism recordings, Pearson correlation coefficients (CC) were calculated between the DF microseisms and ocean wave heights recorded at selected buoys in each frequency band.
