Reverse-Time Migration Imaging of GPR Data Based on Local Nyquist Attenuation Compensation Cross Correlation Imaging Condition

Reverse time migration (RTM) can accurately simulate electromagnetic wave propagation in complex media and has become an essential technique for high-resolution ground penetrating radar (GPR) imaging. However, the conventional full-wavefield storage cross-correlation imaging condition (CIC) requires the complete source wavefield time history to be stored, resulting in excessive memory and I/O costs. Although the excitation amplitude imaging condition (EAIC) can substantially reduce storage requirements, it often causes energy loss and imaging instability in highly lossy or noisy environments. To strike a better balance between imaging accuracy and computational efficiency, this study proposes a Nyquist local attenuation compensation cross-correlation imaging condition (NLACCIC). In this method, only locally sampled forward wavefields that satisfy the Nyquist criterion are stored during forward propagation, enabling sparse yet efficient wavefield storage. During the backward propagation of the adjoint field, numerical attenuation compensation is achieved by reversing the sign of the conductivity term, effectively restoring and enhancing deep reflection energy. Synthetic four-layer models, noise-contaminated data, and field data were used to validate the proposed approach. The results demonstrate that NLACCIC preserves imaging accuracy while significantly reducing storage demand—by 95.72% in synthetic tests and 92.58% in field data, and shortens computation time by 11.70% and 3.94%, respectively. Moreover, it outperforms CIC and EAIC in deep reflection recovery and noise robustness. The proposed NLACCIC provides an efficient and practical solution for large-scale, high-resolution GPR RTM imaging.