## 3 Data and Method  
The investigation focuses on the central deep depression of the Gaoyou Sag, where the study area encompasses 81 drilling and logging wells, including 28 cored wells yielding a total core length of 1080 m. The 3D seismic dataset exhibits dominant frequency ranges of 20-30 Hz, providing effective coverage across 240 km\({}^{2}\) (red rectangle in Figure 1).  
The 3D seismic data acquisition and processing for the central deep depression of the Gaoyou Sag were carried out through a systematic and multi-step workflow to ensure high-quality subsurface imaging. Seismic sources, including vibrator trucks, were strategically deployed across the 240 km\({}^{2}\) survey area, with seismic receivers arranged on the surface and in boreholes to ensure comprehensive spatial coverage. The seismic frequency range of 20-30 Hz was selected to capture high-resolution data from the target depth, considering the complex geological conditions. Preprocessing steps, including noise suppression, static correction, and time-to-depth conversion, were essential for enhancing the clarity and accuracy of the data. Seismic imaging employed conventional stacking and advanced depth migration methods to account for the structural complexities of the region, allowing for precise subsurface modeling. The final 3D seismic volume was integrated with core and logging data from 81 wells, including 28 cored wells, to validate and refine the interpretation. This integration enabled the identification of key geological features and hydrocarbon reservoirs, providing a solid foundation for further seismic sedimentological research and exploration-development in the Gaoyou Sag.  
Building upon seismic stratigraphy and seismic sedimentology, this investigation has achieved substantial improvements in the recognition and interpretation of depositional system tracts through the implementation of high-resolution striatal slice imaging techniques [1,15,16]. Compared to conventional seismic profile analysis, the proposed methodology demonstrates interpretation fidelity approaching core-scale resolution under specific lithost stratigraphic conditions, therefore effectively reducing the seismic interpretation cycle by 32-45% in case study applications. The progressive development of 3D seismic exploration technologies and interpretation workflows has positioned seismic sedimentology as an indispensable analytical tool for basin evolution studies, system tract analyses, reservoir characterization, and hydrocarbon accumulation pattern analyses.  
As an emerging post-stack seismic processing and interpretation method, spectral decomposition relies on the thin-bed tuning principle, serving as a critical tool for seismic sedimentological investigations. This technique transforms time-domain seismic data into frequency-domain representations through wavelet or Fourier transforms. Under the assumptions of constant seismic velocity, high-frequency components are sensitive to thin-bedded strata, whereas low-frequency responses primarily reflect thick-bed tuning characteristics. For sandbodies of indeterminate thickness, systematic frequency scanning identifies tuning-compliant frequencies, enabling thickness inversion through velocity-frequency relationships, thereby facilitating thin-bed detection [7, 8, 9, 10].