## 4 Results
### Seismic Response Characteristics of Sedimentary Facies  
By integrating existing geological survey data and conducting comprehensive analyses of well logging, logging while drilling, and seismic profiles, we have developed a depositional facies model for the study area that includes four primary rock facies types: lacustrine, braided river delta, fan delta, and volcanic. The lacustrine facies acts as a significant background depositional facies in the Changling Graben, with seismic characteristics primarily displayed as parallel or sub-parallel, sheet-like reflection structures. The braided river delta facies is predominantly found on the gentle short-axis slopes or the narrow long-axis flanks of the graben, and its seismic response is marked by prograding, hummock, or sheet-like reflection structures. The fan delta facies mainly develops along the side of the controlling depression fault, with seismic signatures typically presenting as hummocky wedge-shaped or discontinuous hummocky hill-shaped reflection structures. The volcanic facies, widely distributed within the Huoshiling and Yingcheng formations, often exhibit distinct arched, cone-shaped chaotic reflection structures on seismic profiles.  
By integrating the distribution of denudation and sedimentary facies analysis (Figure 11) and using the depositional period of the Shahezi Formation as a case study, it is evident that the basin's structure during this era was profoundly influenced by the boundary fault-controlled depression. Intense graben activity resulted in the formation of multiple lake basins within the Changling Graben, which are classified as key background sedimentary facies of the Graben period. These can be categorized into marginal shallow lake, semi-deep lake, and deep lake subfacies. Driven by sediment supply from the Gudian Uplift and Shenzijing Uplift, small-scale fan delta deposits formed along the fault sides of each subordinate graben lake basin, transitioning to marginal shallow lake deposits towards the lake centers. The gentle short-axis slope of the Gudian Graben fostered the development of a braided river facies. Except for the central Trough, which extends continuously from Qianbei to Shenzijing to Chaganhua Trough, all other subordinate Troughs are distinctly segmented, creating a characteristic pattern of alternating depressions and uplifts [19; 20]. Aligning with the denudation range, the differential uplift and subsidence of strata on either side of the controlling fault caused the upper plate strata to rapidly subside, accepting sedimentation, and leading the graben to evolve from initial compensation sedimentation to under-compensation sedimentation. This transition resulted in the deepening of water bodies and a swift shift to semi-deep to deep lake environments, triggering striatal onlap phenomena. Fan delta and braided river delta sand bodies developed on the steep and gentle slopes of the trough, respectively. Towards the end of the Shahezi Formation's depositional period, the basin transitioned into a rapid graben phase, marked by localized compression, uplift, and denudation, predominantly within the semi-deep to deep lake zones. Denudation intensified from the depositional center outwards, peaking on the slopes and then gradually diminishing. This pattern corresponds to areas where under-compensation sedimentation was succeeded by compressional uplift and denudation. The reconstructed outcomes, synthesized from lithological and seismic facies data, align with the sedimentary facies, thereby validating the precision of the denudation volume restoration.