信噪比和炮点方位对海底电缆方位角求取精度的影响

海底电缆三分量检波器的布设通常采用拖放方式，因受海流、船速等因素影响，其两个水平分量难以完全与设计方位重合。为了精确求取方位角，需对两个水平分量的方位角做高精度分析，并获取不同情形下的方位角误差。本文基于二维数据分析了不同噪声水平下的方位角误差，基于三维数据分析了不同方位角和不同噪声水平双因素影响下的方位角误差，并得出结论：如果在X和Y分量某道的直达波时段给定一个时窗，则X和Y分量对应采样点数据满足线性关系；在不考虑方位角自身因素影响的条件下，方位角误差随信噪比的增大而减小；当已知实际资料的信噪比时，可求出方位角误差范围；在信噪比较低时，靠近坐标轴方向计算的方位角误差最小；随着信噪比由低增高，最小角度误差区域由靠近坐标轴方向向各象限45°角方向分散。

Impacts of SNR and shot point locations on calculation precision of ocean bottom cable azimuth

Three-component ocean bottom cables are usually deployed by drag-and-drop approach. With the influence of ocean currents and board speeds, the azimuth of two horizontal components of sensors cannot be fully the same as the designed azimuth. In order to have the precise azimuth, azimuth deviation of two horizontal components should be calculated. This paper analyzes angular deviations under different noise levels for 2D data, and angular deviations under different azimuths and different noise levels for 3D data. In a time window of a trace, direct wave samples on X and Y components have a linear relation. Without considering the influence of azimuth factors, the azimuth deviation decreases with SNR increase. The azimuth deviation range can be calculated with a known SNR of seismic data. The azimuth deviation close to the axis direction is minimum when SNR is low. As SNR increases, the minimum azimuth deviation distracts with 45 degree angle directions from the axis.