Research on Non-intrusive Detection of Marine Sediment Cores Using Magnetic Induction Tomography

The physical characterization of marine sediment cores is pivotal for the exploration of shallow seafloor resources, such as gas hydrates and shallow gas. While non-intrusive imaging is essential for preserving sample integrity, conventional detection methods face significant limitations. Although X-ray CT offers high-resolution imaging, its application is constrained by bulky instrumentation and time-consuming scanning processes, rendering it impractical for rapid, on-site evaluation of sediment cores. Conversely, Electrical Resistivity Tomography (ERT) offers high sensitivity to electrical properties but relies on contact measurements. This inevitably disturbs the original structure of unconsolidated sediments and suffers from electrode polarization, thereby degrading imaging quality.

To address these challenges, this study investigates a non-intrusive imaging technique based on Magnetic Induction Tomography (MIT) to probe the internal electrical conductivity structure of sediments. In this method, excitation coils surrounding the core are energized with time-harmonic alternating current to generate a primary magnetic field. According to the principle of electromagnetic induction, eddy currents are induced within the conductive sediment, subsequently generating a secondary magnetic field that opposes the primary one. Since the intensity and path of these eddy currents are strictly governed by the spatial distribution of conductivity within the core, the internal structural information can be retrieved by detecting the perturbed total magnetic field via an array of receiver coils.

The feasibility of this proposed method was validated through forward modeling based on the Finite Element Method. To reconstruct the conductivity distribution from the magnetic measurements, the inverse problem was solved using the Gauss-Newton method. Preliminary simulation results demonstrate that the magnetic induction-based approach can effectively recover the internal electrical structure of the target, confirming its potential as a compact and efficient tool for marine sediment characterization.

This work was supported by the National Natural Science Foundation of China, Grant No. 42274232.