Three-Dimensional Inversion and Interpretation of Multimodal Geophysical Data in Yamagawa Geothermal Field, Japan

Summary Exploration and development of geothermal fields requires quantitative interpretation of different geophysical data. In this paper, we introduce the novel approach to three-dimensional inversion and interpretation of multimodal geophysical data, which incorporates the known geological/geophysical constraints. In a general case, geophysical inverse problem is ill-posed, i.e., it is non-unique and unstable; however, appropriate a priori information can help reducing the nonuniqueness and increasing the stability of this ill-posed problem. The developed approach uses the principles of inversion “guided” by known information. In the framework of this approach, the 3D inversion itself is data driven, but a priori geological/geophysical model is used as the initial and reference model during the iterative inversion process. We have applied the developed method to the integrated interpretation of magnetotelluric, gravity, and magnetic data in Yamagawa geothermal field of Japan, using the constraints based on seismic and well-logging data acquired in the same area. The results have demonstrated that the developed method produces reliable 3D models of different physical properties, which provide a solid basis for geological interpretation of the complex subsurface structures in the survey area, critical for geothermal exploration.