Correction of water column height variation on 2D grid high‑resolution seismic data using dGPS based methodology@en

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.水柱物理性质的差异往往会对高分辨率地震数据的精确水柱高度校正造成阻碍，该问题在浅海环境采集的地震数据中尤为突出。水柱性质的变化可归因于潮汐与海流波动、风浪生成的涌浪、长短振幅波前，以及盐度与水温的差异。与此同时，作业船舶的自身运动也会加大水柱高度的解算难度。本研究提出了一种耗时更短且精度更高的基于差分全球定位系统（Differential Global Positioning System, DGPS）的校正方法，该方法可适用于绝大多数类型的高分辨率地震数据，从而显著提升小深度尺度下推导得到的地质解译结果的追踪精度与质量。该方法已在北海德国管辖海域获取的地球物理剖面中完成了测试验证。本次研究的核心目标是在分米级尺度下，识别、区分并分类地层高度复杂的浅海环境中的各类地下沉积构造。对剖面完成校正后，整体而言海底的实际埋深较未校正剖面结果深1.1至3.4米（平均埋深2.2米），与已发表的经潮汐校正的水深测量数据所得海底高程一致。校正后的地震剖面被用于绘制全新世河道构造基底的埋深，并确定其坡度梯度。该校正方法在区分冰川期与冰后期河谷特征、开展剖面间对比，以及构建研究区构造与地层格架方面同样发挥了关键作用。