Velocity-independent NMO correction based on multi-scale dynamic time warping

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Normal moveout (NMO) correction is one of the common steps of seismic data processing. Conventional NMO correction is generally based on a velocity function, but velocity analysis is considered time-consuming and labor-intensive. Moreover, the field seismic data observed in complex areas can have low signal-to-noise ratio (SNR), resulting in inaccurate picked up velocity parameters and poor NMO correction. The conventional NMO correction has stretching issues, most significantly at shallow and large offset areas. To address these problems, a new multi-scale dynamic time warping (MSD) algorithm for velocity-independent stretch-free NMO correction is investigated. This algorithm has higher accuracy and stronger noise resistance, as our comparisons with other applications of DTW show. In our algorithm, the original seismic data is decomposed into multiple morphological scales (using mathematical morphology theory), and alignment errors are calculated separately at each scale, followed by further adaptive weighted summation. Accumulation and backtracking operations based on alignment errors produce time shift sequences for automatic flattening of the gathers. The effectiveness of the presented approach is tested on both synthetic and field data. The results demonstrate that compared with traditional velocity-based NMO correction methods, the proposed method can accurately flatten seismic gathers without the NMO stretch and is robust to strong noise.