Microseisms and Their Relationship With Solid Earth, Ocean, and Atmospheric Dynamics: Insights From Ocean Bottom Seismometer Observations in the Northern Okinawa Trough-Ryukyu Arc-Trench System

This study investigates the characteristics and generation mechanisms of ocean microseisms in the Northern Okinawa Trough-Ryukyu Arc-Trench System, using continuous recordings from in situ ocean-bottom seismometers and nearby land stations, integrated with the ERA5 climate and ocean reanalysis data sets. The power spectral densities (PSDs) of double-frequency microseisms (DFMs) deviate notably from the classical Peterson's model in the 0.8–4 s period range, suggesting regional noise characteristics that may not be fully captured by global reference curves, especially in complex marine environments. Two distinct DFM peaks are identified at 2–6 s (SPDFM) and 6–10 s (LPDFM), both of which intensify during winter monsoons and typhoons as strong seasonal winds generate high-energy waves that couple efficiently with the seafloor, amplifying microseism activity. SPDFM PSDs correlate strongly with significant wave height (SWH) in marginal seas, such as the East China Sea, where local wave conditions and bathymetric barriers predominantly govern asymmetric energy distributions. In contrast, LPDFM exhibits broader, more symmetrical correlations with SWH, extending into the deeper Philippine Sea and Western Pacific. Single-frequency microseisms (SFM, 10–20 s) display similar patterns but weaker correlations, with both LPDFM and SFM linked to distant swells from the North Atlantic and equatorial Indian Oceans. Polarization analysis indicates that Love waves dominate SPDFM, with contributions from S waves, while sediment cover and topographic features introduce complexity in wave separation. These findings emphasize the role of local and distant wave sources, atmospheric conditions, and bathymetric undulations in modulating microseism generation and propagation, providing a framework for studying atmosphere-ocean-solid earth interactions.