Analysis and 3D inversion of magnetotelluric crooked profile data from central Svalbard for geothermal application

• Published in: Tectonophysics 2016-08, Vol.686, p.98-115
• Main Authors: Beka, Thomas I., Smirnov, Maxim, Birkelund, Yngve, Senger, Kim, Bergh, Steffen G.
• Format: Article
• Language: English
• Subjects: 3D modelling; Arctic bathymetry; Exploration Geophysics; Geothermal exploration; Inversion setting; Magnetotellurics; Prospekteringsgeofysik; Svalbard geology
• ISSN: 0040-1951; 1879-3266; 1879-3266
• DOI: 10.1016/j.tecto.2016.07.024

Broadband (0.001–1000s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS=1.05). The final 3D resistivity model displays a complex geology of the near surface region (2km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (>1000Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (