Max A. Meju

TL;DR: In this paper, magnetotelluric data were used to image two major zones or channels of high electrical conductivity at a depth of 20-40 km from the Tibetan plateau into southwest China, and the electrical properties of the channels imply an elevated fluid content consistent with a weak crust.

TL;DR: In this paper, the Lagrange multiplier method is used to solve the resistivity-velocity cross-gradients problem for a nonlinear least square problem, which leads to resistivity and velocity models with remarkable structural agreement, and the resultant iterative two-dimensional (2-D) joint inversion scheme is successfully applied to synthetic data (serving as validation tests here) and to field data from collocated DC resistivities and seismic refraction profiling experiments.

TL;DR: The role played by the structural gradients-based approach for coupling fundamentally different physical fields in (mainly) geophysical inversion is summarized, further understanding is developed, and the main challenges and directions for future research are defined.

TL;DR: In this paper, a joint 2D inversion approach for imaging collocated magnetotelluric and seismic refraction data with cross-gradient structural constraints is presented. But the results suggest that joint MT-seismic crossgradient imaging leads to improved characterization of heterogeneous geological targets at near-surface to mantle depths.

Abstract: The controlled-source electromagnetic (CSEM) induction method is emerging as a leading geophysical technique in hydrogeological studies. However, the technique is quite often misunderstood compared to other common techniques of applied geophysics: namely, seismic reflection and refraction, magnetics, gravity, and ground-penetrating radar (GPR). In this chapter we review the fundamental physical principles behind the CSEM prospecting technique, with emphasis on near-surface applications, and present some recent advances in this field that have been made by the authors. CSEM methods are defined here to be those in which the experimenter has knowledge of and control over the electromagnetic field transmitted into the ground and hence excludes magnetotellurics, related natural-source methods, and the various uncontrolled-source methods involving, for example, radio transmissions.