Rawlinson, Z.J.; Berhe, D.T.; Herpe, M.; Asif, M.R. 2025 Aqua Intel Aotearoa Phase 3: Southland SkyTEM processing and resistivity modelling. Aqua Intel Aotearoa report 2025/05; GNS Science consultancy report 2025/99. 56 p.
Abstract
In November–December 2022, 5300 km of SkyTEM 312 data were collected in Southland by SkyTEM Australia Pty Ltd. This report describes the processing and resistivity modellingof these data. A recently developed neural network was applied by the Aarhus University HydroGeophysics Group (HGG) to automatically remove electromagnetic noise from the SkyTEM low-moment and high-moment data. Manual data processing and post-processing were then undertaken by GNS to check for any remaining data artefacts, which were subsequently removed and a quality-check undertaken. Using the retained data, spatially constrained inversions were performed, creating both a smooth and a sharp resistivity model result, and a final quality-check was then undertaken by HGG. For each resistivity model, a depth of investigation (DOI) was estimated—resistivity structures below the DOI standard value are very weakly resolved by the data and should normally be disregarded. The resistivity models provide a detailed 3D resistivity picture of the subsurface, and the specifics are as follows: layer thickness of 2 m in the near-surface, increasing to 96 m at 750 m depth; and the standard DOI varies from 25 to 800 m, with a mean of 396 m (standard DOIs were calculated from the smooth resistivity models). This report includes selected images of the resistivity models, and digital datasets havebeen developed to support future work using these data. Data access requires permission from MBIE. Interpolated resistivity maps were created for each layer in the resistivity models in depth. Those with sufficient spatial coverage were added as raster files to ESRI ArcGIS geodatabases, and a layer file was created for immediate use in GIS. The interpolated raster files extend to a depth of 365 m. Hydrogeological interpretation of these resistivity results is required for full utilisation of the information contained in this report; however this subsequent piece of work is not currently funded (auths)
