## 3 Databases and Methods
### Restoration Method of Formation Denudation  
Numerous methods are currently available for calculating stratigraphic denudation, including the stratigraphic structural trend extrapolation method, the acoustic well logging curve method, and the wave equation analysis method [54; 55]. Each method possesses distinct advantages and is applicable under specific conditions. The calculation of stratigraphic denudation must be carefully aligned with the tectonic evolution context of the study area to select the most appropriate method for restoring denudation volumes, thereby ensuring the reliability and applicability of the results [56; 57]. While most of these methods yield denudation data at discrete points, the stratigraphic structural trend extrapolation method emerges as the most effective approach for achieving a comprehensive understanding of the planar distribution of denudation. The acoustic wave time difference method is widely employed for calculating denudation volumes. Initially, we assessed the applicability of this method. The method is based on the assumption that there is a consistent exponential relationship between the acoustic wave time difference in rocks and their depth, provided that the compaction pattern of the strata remains unchanged [58; 59]. By statistically fitting the acoustic wave time difference and depths of undepleted strata, a standard exponential compaction trend curve is derived. Extrapolating this curve to where the acoustic wave time difference (\(\Delta t\)) equals the initial acoustic wave time difference (\(\Delta t_{0}\)) delineates the paleosurface; the interval between this  
Figure 5: Typical seismic profile of Changling Graben (the profile location is shown in Figure 1). Notes: (**a**) original seismic profile; (**b**) seismic interpretation profile. paleosurface and the unconformity represents the denudation thickness (Figure 6). The application of this method is subject to specific criteria. Generally, it is applicable when the pressure exerted by the newer strata above the denudation surface on the underlying residual strata is less than or equal to the pressure exerted by the eroded strata prior to denudation. This ensures the integrity of the compaction curve for the residual mudstones in the lower sections. However, drilling data from the study area reveal that the combined thickness of the graben strata and the overlying newly deposited strata exceeds 500 m, significantly surpassing the thickness of the eroded strata. Additionally, the deposition process was marked by vigorous activity along the controlling fault and the formation of extensive volcanic rocks. Consequently, the logging data do not conform to the expected sedimentation and compaction patterns, making it impossible to generate a reliable compaction curve and, thus, to calculate the denudation thickness. Therefore, the acoustic wave time difference method is not suitable for determining the denudation thickness of the strata in this context. Denudation can lead to the formation of unconformities between stratigraphic layers, with each unconformity potentially indicating multiple phases of uplift and denudation. By integrating the analysis of tectonic activities and regional geological settings within the study area, the stratigraphic structural trend extrapolation method proves to be highly applicable. This methodology utilizes the orientation of residual strata and the convergence trend of co-phase axes to reconstruct the pre-denudation strike, thereby estimating the magnitude and spatial distribution of denudation during key tectonic episodes. It provides a means of quantifying the multi-episodic denudation volumes of the strata [60,61]. The integration of drilling data and 3D seismic data elucidates distinct unconformities between the Huoshiling Formation, Shahezi Formation, Yingcheng Formation, and Denglouku Formation with the overlying strata in the Changling Graben. Particularly in the Shenzijing-Hashitu region, there is a notable disparity in the strike of the overlying and underlying strata.