A reorientation approach for four-component ocean-bottom nodes using first-arrival characteristics

Abstract In multicomponent seabed seismic surveys, sensor azimuthal misalignment is a major source of cross-component interference. Due to irregular seabed topography and ocean currents, actual sensor orientations often deviate from the intended coordinate axes, leading to significant mixing of wavefields among the x-, y-, and z-components. This misalignment reduces the accuracy of wavefield separation and degrades the quality of subsequent elastic-wave imaging. In shallow-water ocean-bottom node (OBN) data, clear direct-wave signals are often absent, and source-generated noise complicates first-arrival picking, rendering traditional direct-wave polarization-based orientation methods ineffective. To address the challenges arising from missing or inaccurate orientation parameters, we propose a precise orientation approach for three-component shallow-water OBN data, based on refracted waves that are widely present and exhibit richer polarization information. We construct a robust objective function that incorporates first-arrival energy distributions, polarization characteristics, and the correlation between the p- and z-components. The objective function is solved iteratively using the beluga whale optimization algorithm, effectively eliminating the ambiguity of multiple solutions caused by axis reversal in conventional methods. The proposed approach was validated on a real dataset from the Shengli Oilfield marine region, and the derived orientation parameters underwent rigorous evaluation and quality control. The results demonstrate that the method achieves high orientation accuracy and robustness.