108 Geophysics in Geothermal Exploration Processing these data often involves simultaneous or joint inversion techniques, such as: • refraction tomography combined with electrical resistivity tomography (ERT), • acoustic impedance inversion paired with controlled-source EM (CSEM), magnetotelluric (MT), or deep ERT. In near-surface studies, multiple methods can be used together to produce a more detailed geological model. For example, combining P-wave refraction tomography with MASW provides both P-wave and S-wave distributions, allowing for the computation of mechanical parameters such as Poisson’s ratio (Pasquet and Bodet, 2017). For deeper targets, seismic reflection methods, which provide both structural and petrophysical information about a reservoir, can be combined with CSEM to detect the presence of hydrocarbons (Alvarez et al., 2017). However, it is essential to calibrate surface geophysical results with borehole measurements, including well log and borehole seismic data. Passive methods, being less invasive and cost-effective, are valuable tools. When combined, passive seismic, MT, and gradiometry can yield a shear velocity model, resistivity distribution with depth, and insights into bedrock location and fault structures. Passive techniques can also identify specific areas for more detailed active seismic surveys and extend coverage where conventional seismic methods are impractical. Overall, the integration of multiple geophysical methods enhances subsurface imaging and offers more reliable insights, enabling more informed decision-making in geological exploration and reservoir characterization. References The writing of the chapter (text and relative figures) is mainly based on the following papers and books. Achenbach J.D. (1973) Wave propagation in Elastic solid, North Holland Publishing Company, 3rd Ed. Alvarez P., Alvarez A., MacGregor L., Bolivar F., Keirstead R., Martin T. (2017) Reservoir properties prediction using controlled-source electromagnetic, prestack seismic, and well-log data: Case study in the Hoop Area, Barents Sea, Norway, Interpretation 5(2), 1-17, https://doi.org/10.1190/INT-2016-0097.1. Archie G.E. (1942) The electrical resistivity log as an aid in determining some reservoir characteristics, Petroleum Technology 1, 55-67.
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