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Abstract

In recent years, 3D inversion has become a practical, if still computationally demanding, tool for interpreting MT data. This interpretation approach appears to hold great promise by overcoming the simplifications necessary to force the 3D nature of the real world into 2D models and thus producing more realistic and truthful images of the subsurface. In a series of geologic situations, however, we can identify a 2D regional structure in which local 3D structures are embedded. Based on synthetic data, we explore the resolution of an elongated highly conductive zone (HCZ) with varying along-strike extents embedded in a 2D regional resistivity structure with 3D and 2D inversion algorithms. Our results show that both inversion approaches recover the HCZ for large along-strike extents; for shorter extents, surprisingly 2D inversion better recovered the subsurface structures. In presence of high conductivity contrasts and wide conductivity contrasts 3D inversion can fail to resolve structures of predominantly 2D character. In 2D inversion, the weak 3D nature of the ocean included in the synthetic model impaired the impedance-only inversion results for short HCZ extent and problems occurred if phase values below 5° were present in the data set.