[SSS03-P02] Incoming directions of broadband infragravity waves observed at the central part of the Pacific Ocean
Keywords:Infragravity wave, Pacific Ocean, Incoming direction
We used 22 DPGs with an array aperture of 600 km and station spacing of ~50 km. The observation periods were (1) from January 2005 to January 2006 and (2) from April 2006 to June 2007. In this study, we used the data from the first observation because the array aperture and station spacing in the first one was suitable for detecting IGWs. For continuous records, we applied a cross-correlation technique with one-bit normalization, and estimated incoming directions of IGWs using the calculated cross-correlation functions (CCFs) at frequency bands of 0.5 –1 mHz, 1–2 mHz, 2–10 mHz, and 10–20 mHz by assuming that IGWs wavefront is planar.
For the CCF, we changed the stacking time length of CCFs to detect IGW propagations. As a result, IGWs could not be retrieved in the 1-day averaged CCFs, but they emerged in the 30-day CCFs in the four frequency bands. Our results on the incoming IGW direction show that long-period IGWs (0.5–1 mHz) are coming from all directions in boreal winter and between east and south in boreal summer, while short-period IGWs (10–20 mHz) are coming between north and east in boreal winter and between east and south in boreal summer. This means that the IGW characteristics between long and short periods in boreal summer are consistent, but in boreal winter are significantly different. To investigate the excitation and seasonal variations of IGWs more details, the calculation of ray paths would be required.
The DPG data was acquired by The Hawaiian PLUME Project, and was downloaded by Incorporated Research Institutions for Seismology (IRIS) (https://www.iris.edu/hq/).