The force system can be attributed to topographic coupling between the seismic waves and ocean waves (i.e., infragravity wave at the ocean floor for seismic hum, (13,143) and to ocean swell in near-shore areas for primary microseisms.
(2012) Infragravity wave source regions determined from ambient noise correlation.
Below 1 Hz, the dominant source of this wave field is oceanic gravity waves (specifically, ocean swell, wind waves, and ocean infragravity waves).
Watada and Masters (2001) pointed that ocean infragravity waves excite seismic hum based on observation of ocean bottom pressure gauge.
The researchers used seismic data collected on the Ross Ice Shelf to identify signals generated by infragravity waves that originated along the Northern California and British Columbia coasts, and modeled how much stress an ice shelf suffers in response to infragravity wave impacts.
"Whether increased infragravity wave frequency and energy induced by heightened storm intensity associated with climate change ultimately contribute to or trigger ice shelf collapse is an open question at this point," said Bromirski.
According to Bromirski, storm-driven ocean swells travel across the Pacific Ocean and break along the coastlines of North and South America, where they are transformed into very long-period ocean waves called "infragravity waves" that travel vast distances to Antarctica.
Bromirski, along with his colleagues, has proposed that the southbound travelling infragravity waves "may be a key mechanical agent that contributes to the production and/or expansion of the pre-existing crevasse fields on ice shelves," and that the infragravity waves also may provide the trigger necessary to initiate the collapse process.
The study also found that the interaction between bores and smaller, longer waves known as infragravity waves
creates a large portion of the momentum that drives extreme wave run-up.
where [u.sub.w] is the steady current driven by breaking waves, [u.sub.t] is the tidal current (this is not the case of the Black Sea where this component can be neglected), [u.sub.a] is the wind-driven current, and [u.sub.o] and [u.sub.i] are the oscillatory flows due to wind waves and infragravity waves
(1993) Beach erosion in a storm due to Infragravity waves
. Report of the Port and Harbour Research Institute 31, 73-102.
Previous studies had found that this hum is excited by infragravity waves
, a type of ocean wave that originates in shallow water along coasts, but it was uncertain whether hum is generated primarily by infragravity waves
in the deep ocean or along coastlines.