UACE2017 Proceedings: Bottom-diffracted surface-reflected arrivals in the North Pacific

Session:
Three-dimensional sound propagation models and effects
Paper:
Bottom-diffracted surface-reflected arrivals in the North Pacific
Author(s):
Ralph Stephen
Abstract:
Bottom-diffracted surface-reflected (BDSR) arrivals were first identified in the 2004\nLong-range Ocean Acoustic Propagation Experiment (LOAPEX) in the North Pacific (Stephen et\nal, 2013, JASA, v.134, p.3307-3317). In deep water, ambient noise and PE predicted arrivals are\nsufficiently quiet that BDSR paths, scattered from small seamounts, can be the largest amplitude\narrivals observed. The Ocean Bottom Seismometer Augmentation in the North Pacific\n(OBSANP) Experiment in June-July 2013 studied BDSRs at the same site in detail. They are\nmost readily identified by their move-out on lines of transmissions and are clearest on the\nvertical component channel. There appear to be two classes of diffractors. The diffraction points\nfor Type 1 BDSRs occur substantially out of the source-receiver sagittal plane, a true 3-D\ndeterministic scattering effect. The diffraction points for Type 2 BDSRs are essentially in the\nsource-receiver sagittal plane, a 2-D scattering effect. The diffraction points for BDSRs occur\nboth on the sides of small seamounts and on the relatively featureless deep seafloor. In at least\none case the same BDSR is observed for 77.5, 155 and 310Hz M-sequence transmissions. Work\nsupported by ONR.
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