scholarly journals Range‐depth ambiguity surfaces for vertical arrays in shallow‐water environments

1987 ◽  
Vol 81 (S1) ◽  
pp. S64-S64
Author(s):  
Richard Heitmeyer ◽  
Rachel Hamson
Keyword(s):  
Shallow Water ◽  
Vertical Arrays

Stone rosettes as indicators of ancient shorelines: examples from the Precambrian Belcher Group, Northwest Territories

1979 ◽  
Vol 16 (9) ◽  
pp. 1887-1891 ◽  
Author(s):  
B. D. Rlcketts ◽  
J. A. Donaldson
Keyword(s):  
Shallow Water ◽  
Northwest Territories ◽  
Close Packing ◽  
Desiccation Cracks ◽  
Cross Bedding ◽  
Vertical Arrays ◽  
Water Origin ◽  
Shallow Subtidal ◽  
Shore Platforms

Flat-pebble conglomerates in the McLeary Formation of the Belcher Group display close packing of intraformational slabs in near-vertical arrays that appear distinctively polygonal in sections parallel to bedding. Such arrangements of flat pebbles, known by names such as stone rosettes and slone packings, are common on modem beaches, especially within the swash and backwash zone of shore platforms. Association of the McLeary stone rosettes with sedimentary features suggestive of shallow subtidal to supratidal origin (herringbone cross-bedding, reactivation surfaces, desiccation cracks, tepee structures, gypsum casts, oncolites, stromatolites, and probable beachrock) supports a hydrodynamic origin for these polygonal arrays of flat pebbles, an origin that has been demonstrated for modern occurrences. Where associated structures corroborate interpretation of a shallow-water origin, such stone rosettes provide evidence for ancient strandlines, and the designation "beach rosettes" is suggested as appropriate to distinguish them from stone rosettes formed by periglacial processes.

MODE AND WAVENUMBER INVERSION IN SHALLOW WATER USING AN ADJOINT METHOD

2004 ◽  
Vol 12 (04) ◽  
pp. 521-542 ◽  
Author(s):  
ISABELLE CHARPENTIER ◽  
PHILIPPE ROUX
Keyword(s):  
Shallow Water ◽  
Adjoint Method ◽  
Automatic Differentiation ◽  
Pressure Field ◽  
Water Environment ◽  
Specific Treatment ◽  
Oceanic Waveguide ◽  
New Approach ◽  
Vertical Arrays ◽  
Shallow Water Environment

Modes and wavenumbers are the principal ingredients that characterize the pressure field in an oceanic waveguide. However, wavenumber and mode inversions are well-known to be a difficult task in underwater acoustics. Moreover, this double inversion has never been performed simultaneously from the same configuration of emitters and receivers. We present a new approach to this problem in a shallow water environment between two vertical arrays of sources and receivers. Starting from a classical modal decomposition of the pressure field, our algorithm focuses on a specific treatment of phase and amplitude variables. The key idea is to run a three-stage optimization by working separately on the phase and amplitude of the acoustic field. The high number of variables of the problem is turned into an advantage by using an adjoint code generated by an Automatic Differentiation software. Numerical results in the presence of noise show that modes and wavenumbers are estimated with a high accuracy.

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