Abstract
Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments. Changes in water column properties can be attributed to variation in tides and currents, wind-generated swells, long and short amplitude wave-fronts, or variation in salinity and water temperature. Likewise, the proper motion of the vessel complicates the determinability of the water column height. This study provides a less time-consuming and precise differential Global Positioning System based methodology that can be applied to most types of high-resolution seismic data in order to significantly improve the tracking and quality of deduced geological interpretations on smaller depth scales. The methodology was tested on geophysical profiles obtained from the German sector of the North Sea. The focus here was to identify, distinguish and classify various sub-surface sedimentary structures in a stratigraphically highly complex shallow marine environment on decimeter small-scale. After applying the correction to the profiles, the sea floor, in general, occurs 1.1 to 3.4 m (mean of 2.2 m) deeper than the uncorrected profiles and is consistent with the sea floor from published tide corrected bathymetry data. The corrected seismic profiles were used in plotting the depth of the base of Holocene channel structures and to define their gradients. The applied correction methodology was also crucial in glacial and post-glacial valley features distinction, across profile correlation and establishing structural and stratigraphic framework of the study area.
Highlights
Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments
The physical properties of water column such as density, state of occurrence among others can change significantly over a short period of time. This poses a great challenge on seismic data acquired offshore as a series of independent 2D or 3D seismic grid over time. These changes in the physical properties of water column may result in inaccurate interpretation of geologic features in the sub-sea floor in cases where differences in depth on decimeter scale are critical for the relative stratigraphic classification of morphologic sub-surface structures
This paper demonstrates the effectiveness of a differential Global Positioning System based methodology in correcting water column height variations using 87 ultra-high-resolution seismic profiles acquired from the shallow German North Sea sector as examples (Fig. 2)
Summary
Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments. Changes in water column properties can be attributed to variation in tides and currents, wind-generated swells, long and short amplitude wave-fronts, or variation in salinity and water temperature. This poses a great challenge on seismic data acquired offshore as a series of independent 2D or 3D seismic grid over time These changes in the physical properties of water column may result in inaccurate interpretation of geologic features in the sub-sea floor in cases where differences in depth on decimeter scale are critical for the relative stratigraphic classification of morphologic sub-surface structures. Changes in water column properties can be attributed to variation in tides and currents, windgenerated swells, long and short amplitude wave-fronts, variation in salinity and water temperature, pitch, tilt and roll of ship and/or combination of these factors. These structures can often be distinguished and interpreted only by precise analyses of their altitude in the sediment or their gradients
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