## 3 Data and Methods
### Color Fusion of Frequency Decomposition Data
#### 3.4.2 Principle of Color Fusion  
The red-green-blue mode (abbreviated as RGB) is currently one of the most widely used color modes. This mode establishes a two-dimensional color system based on three primary colors: red, green, and blue. It can be understood as the combination of these three primary colors in varying proportions and intensities. The brightness of each primary color can take any value between 0 and 255, allowing the RGB mode to display a total of 16,776,216 (which is 256\({}^{3}\)) colors. Among these colors, the area where all three primary colors are at maximum brightness is white. In practical applications, the three selected attributes correspond to the three primary colors, and they are assigned different weights according to Formula (3). The brightness is used to represent the magnitude of the combined attribute value, thereby facilitating the identification of sedimentary characteristics and the understanding of sand body distribution patterns [65; 66; 67].  
The core concept of RGB frequency division fusion technology lies in the application of frequency division processing and optimization of the original seismic data volume. This is followed by RGB fusion display on the attributes or slices of the same layer from the three frequency division bodies. By employing frequency division, the three-dimensional seismic data volume is transformed into four dimensions and subsequently re-transformed into a three-dimensional data volume through RGB fusion display. This process involves adjusting the chroma of red, blue, and green. Compared to a single attribute or slice, the fusion result provides enhanced emphasis on the boundary between different lithologies. Additionally, it enables the differentiation of various geological bodies based on color. The brightness of a color marked on the fusion slice reflects changes in lithology, while the chroma reflects variation in thickness and period. Consequently, RGB fusion technology proves highly beneficial in exploring the superposition relationship between reservoir  
Figure 4: Seismic profiles of different frequency dividers. (**a**) Original seismic profile, (**b**) 45 Hz frequency division seismic profile, (**c**) RGB fusion seismic profile.  
boundaries and fan bodies, and it provides more abundant and accurate information for the plane characterization of deposition.  
\[\text{C (x,y,z)}=\text{C (IR (x,y,z), IG (x,y,z), IB (x,y,z))} \tag{3}\]  
In the aforementioned formula, C (x,y,z) is the color value after multi-attribute fusion, dimensionless; IR (x,y,z), IG (x,y,z), and IB (x,y,z) are the weights of the three attributes corresponding to the three primary colors, respectively.  
In this study, RGB color fusion is used with the method of frequency decomposition. Three frequency decomposition results are fused and displayed with a 3D color bar. The color fusion result is used to show the change in amplitude in the 3 frequency decomposition seismic cubes both in the section and on the plane. Figure 4 shows the comparison of the original seismic profile (a), 45 Hz frequency division profile (b), and RGB fusion profile (c). The amplitudes of seismic bodies at different frequencies including 20 Hz, 45 Hz, and 70 Hz are color-mapped to red, green, and blue, which represent thick-, medium-, and thin-layer sand bodies, respectively. RGB fusion display is performed on the three single-frequency bodies, and the obtained seismic profile (Figure 4c) shows the thickness information through bright and dark tones. Taking the S32 sublayer as an example, the (Figure 4c) result indicates that the high-brightness white area is consistent with the thick sand body (Figure 4). As the shale content increases, the brightness gradually decreases.