Bathymetric Artifacts in Sea Beam Data: How to Recognize Them and What Causes Them

Sea Beam multibeam bathymetric data have greatly advanced understanding of the deep seafloor. However, several types of bathymetric artifacts have been identified in Sea Beam's contoured output. Surveys with many overlapping swaths and digital recording on magnetic tape of Sea Beam's 16 acoustic returns made it possible to evaluate actual system performance. The artifacts are not due to the contouring algorithm used. Rather, they result from errors in echo detection and processing. These errors are due to internal factors such as side lobe interference, bottom-tracking gate malfunctions, or external interference from other sound sources (e.g., 3.5 kHz echo sounders or seismic sound sources). Although many artifacts are obviously spurious and would be disregarded, some (particularly the “omega” effects described in this paper) are more subtle and could mislead the unwary observer. Artifacts observed could be mistaken for volcanic constructs, abyssal hill trends, hydrothermal mounds, slump blocks, or channels and could seriously affect volcanic, tectonic, or sedimentological interpretations. Misinterpretation of these artifacts may result in positioning errors when seafloor bathymetry is used to navigate the ship. Considering these possible geological misinterpretations, a clear understanding of the Sea Beam system's capabilities and limitations is deemed essential.

[1]  Frank Aikman,et al.  The distribution of geothermal fields on the Juan de Fuca Ridge , 1985 .

[2]  R. Ballard,et al.  The Galapagos Rift at 86° W: 4. Structure and morphology of hydrothermal fields and their relationship to the volcanic and tectonic processes of the Rift Valley , 1980 .

[3]  J. Nriagu,et al.  Selenium pollution of lakes near the smelters at Sudbury, Ontario , 1983, Nature.

[4]  M. C. Kleinrock,et al.  Microplate tectonics along a superfast seafloor spreading system near Easter Island , 1985, Nature.

[5]  J. Mammerickx.  The morphology of propagating spreading centers: New and old , 1984 .

[6]  M. Glenn.  Introducing an Operational Multi-Beam Array Sonar , 1970 .

[7]  K. Crane.  Structure and Tectonics of the Galapagos Inner Rift, 86°10'W , 1978, The Journal of Geology.

[8]  R. Patterson,et al.  Relationships between Acoustic Backscatter and Geological Characteristics of the Deep Ocean Floor , 1969 .

[9]  S. P. Miller,et al.  Sea Beam/Deep-Tow Investigation of an active oceanic propagating rift system, Galapagos 95.5°W , 1986 .

[10]  C.L. Dolph,et al.  A Current Distribution for Broadside Arrays Which Optimizes the Relationship between Beam Width and Side-Lobe Level , 1946, Proceedings of the IRE.

[11]  P. J. Fox,et al.  East Pacific Rise from Siqueiros to Orozco Fracture Zones: Along‐strike continuity of axial neovolcanic zone and structure and evolution of overlapping spreading centers , 1984 .

[12]  P. J. Fox,et al.  Overlapping spreading centres: new accretion geometry on the East Pacific Rise , 1983, Nature.

[13]  Harold K. Farr,et al.  Multibeam bathymetric sonar: Sea beam and hydro chart , 1980 .

[14]  Robert J. Urick,et al.  Principles of underwater sound , 1975 .

[15]  P. J. Fox,et al.  The evolution of craters and calderas on young seamounts: Insights from SEA MARC I and Sea beam sonar surveys of a small seamount group near the axis of the East Pacific Rise at ∼10°N , 1984 .

[16]  Robert D. Ballard,et al.  The East Pacific Rise near 21°N, 13°N and 20°S: inferences for along-strike variability of axial processes of the Mid-Ocean Ridge , 1983 .

[17]  V. Renard,et al.  Sea Beam, Multi-Beam Echo-Sounding in "Jean Charcot" - Description, Evaluation and First Results , 1979 .

[18]  R. Ballard,et al.  Geologic Processes of the Mid-Ocean Ridge and their Relation to Sulfide Deposition , 1983 .

[19]  C. Moustier.  Inference of manganese nodule coverage from Sea Beam acoustic backscattering data , 1985 .

[20]  G. Moore,et al.  Sediment Accretion and Subduction in the Middle America Trench , 1985 .

[21]  T. H. Andel,et al.  The Galapagos Rift at 86°W: 2. Volcanism, structure, and evolution of the Rift Valley , 1979 .

[22]  C. Clay,et al.  Acoustical Oceanography : Principles and Applications , 1977 .

[23]  Peter Lonsdale,et al.  Overlapping rift zones at the 5.5°S offset of the East Pacific Rise , 1983 .

[24]  Christian de Moustier,et al.  Beyond bathymetry: Mapping acoustic backscattering from the deep seafloor with Sea Beam , 1986 .

[25]  R. Arvidson,et al.  Digital image processing of Seabeam bathymetric data for structural studies of seamounts near the East Pacific Rise , 1984 .

[26]  D. Naar,et al.  Fast rift propagation along the East Pacific Rise near Easter Island , 1986 .

[27]  K. Macdonald.  Overlapping spreading centres on East Pacific Rise , 1983, Nature.

[28]  Bernard Widrow,et al.  Principles and Applications of Adaptive Filters: A Tutorial Review, , 1977 .