Fig. 2
From: Seismic noise between 0.003 Hz and 1.0 Hz and its classification
Spectral characteristics of primary microseism and secondary microseism at three locations, YBH in California, USA (top), HRV near the east coast of USA (middle), and CTAO in the northeastern part of Australia (bottom). Monthly averages are shown in different colors. Spectral shapes of the secondary microseism (0.1–0.4 Hz) vary greatly from location to location which in most cases reflect the behavior of ocean waves in the nearby ocean