Insights into infragravity waves in the Pacific Ocean derived from DONET observations

Using continuous seismic data recorded by the broadband ocean bottom seismometer network of the Dense Ocean-floor Network system for Earthquakes and Tsunamis (DONET), this study examines the energy trends of infragravity (IG) waves propagating across the Pacific Ocean. The DONET stations, located in the Nankai seismogenic zone off the southern coast of Japan, are deployed at water depths ranging from approximately 1000 to 4000 m, providing a unique vantage point for IG wave observations. Spectral analysis of the data collected from 2017 to 2019 reveals that IG waves detected at DONET stations are confined to frequency bands between 0.005 and 0.03 Hz, with their peak frequencies and energy levels heavily influenced by water depth. Using cross-correlation beamforming and back-projection techniques, we identify that the primary excitation of IG waves traveling across the Pacific Ocean originates from the coastal zones of southwestern South America and the Pacific-facing side of Antarctica. Secondary excitation of IG waves, which can be generated both distantly and regionally along the Pacific Rim. In recent years, IG wave energy has been observed to be more influenced by dynamic weather events, such as tropical cyclones (TCs), than by seasonal variations. Our findings demonstrate that TCs amplify IG waves across all water layers and generate prolonged impacts that persist for several days after landfall. This highlights a notable interaction between TCs and ocean dynamics, offering novel insights into the behavior of IG waves during extreme weather events. • Infragravity (IG) waves consistently influence offshore areas near Japan. • Primary IG waves originate along South America's and Antarctica's Pacific coasts. • Secondary waves form along the Pacific Rim and intensify in boreal summer. • Tropical cyclones leave lasting effects on IG waves in the ocean. • IG wave energy varies more with dynamic weather events than with seasonal cycles.