## 3 Integrated Geophysical Exploration Techniques for Earth and Rock Dams
### Objective Basis for Data Fusion and Joint Interpretation  
The fusion of multiple information has been a hot issue in the field of geographic information science. Due to the various geophysical methods, which can be understood as conceptual artifacts designed to balance simplicity and complexity, the data acquired inherently reflect a higher degree of structured complexity compared to the more straightforward data sequences obtained by conventional sensors. This structured interplay facilitates the effective management of intricate geological problems by distilling actionable simplicities from complex adaptive systems [105]. To use this information effectively, joint inversion techniques and data fusion methods are required in geophysics. The integrated geophysical exploration information fusion technology proposed in this paper involves studying a data fusion analysis and joint interpretation method for multiscale and multi-physical fields geophysical exploration data through a comprehensive analysis of the data. With this, the unified joint interpretation expression for multiple geophysical parameters is established, and the integrated geophysical exploration research is extended to studies on the internal laws of multiple data. Our team has been working on the analysis of seepage hazards in earth and rock dams for many years based on the monitoring data and engineering characteristics of several domestic and foreign water conservancy and hydropower projects [106]. In terms of seepage and structural analysis, numerical simulation techniques are applied for the inverse analysis of the location and causes of leakage in the body and foundation of dams [107]. To enrich the organic combination of monitoring, detection, and numerical simulation, it is proposed to combine the theoretical study of numerical analysis with integrated geophysical exploration techniques. The theoretical model of the integrated geophysical exploration information fusion technology based on data fusion and joint interpretation was proposed, and experimental research has been carried out in conjunction with related projects. Data fusion and joint interpretation require different physical phenomena of the same target to have certain interrelationships. There are two reasons why multi-physical field detection data can meet the requirements of data fusion and joint interpretation. First, there is an objective relationship between the different parameters of the study object. Second, there is a complementarity between seismic data and electrical and electromagnetic data at different scales. (1) Objective links between physical parameters  
The properties of the same rock (soil) body measured using different physical methods may be different, and different physical parameters can be used to study and describe the physical characteristics of the rock and soil using force, heat, light, electricity, and magnetism as a simple classification. Table 2 presents the relationships between the most common mechanical elastic parameters and electrical parameters in geophysical exploration, obtained by analyzing the objective links existing between various physical parameters. Equation 1 in Table 2 is the Alchian equation, which relates the electrical properties with the water content saturation. Equation 2 is the Faust formula, which represents the relationship between the velocity and resistivity. Combined with the above table, there is an objective basis for the relationship between the rock (soil) parameters, including the electrical and elastic parameters. (2) Complementarity of physical parameters at different scales  
Joint inversion is the result of a series of data complementing each other in the frequency domain. After the geophysical data are converted to the frequency domain, for rock (soil) bodies, the compaction pattern of rock (soil) bodies has a low frequency, the average impedance has a low frequency, and the change in the sand-to-mudstone ratio has a high frequency.