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Joint Inverse Results Using Magnetotelluric and Helicopter-Borne Transient Electromagnetic Data Over a Blind Geothermal System in East Hawthorne, NV, USA
Matthew FOLSOM, Stefano GARANZINI, Tom KIMURA, Carsten SCHOLL
[Geologica Geothermal Group, USA]
A blind geothermal system located in East Hawthorne, NV became a focus of the recent BRIDGE program, a DOE-funded effort to improve exploration workflows and outcomes at discovering and charactering blind geothermal systems in the Basin and Range province. In an effort to characterize this system, the program flew a network of helicopter-borne transient electromagnetic surveys (HTEM) over the prospect, and also collected 61 broadband magnetotellurics stations (MT) over the same field. After modelling both datasets independently, the program then conducted a novel, single-domain joint inversion of the two datasets using new toolkits provided by Viridien. This approach offers the chance to recover a resistivity structure with improved shallow resolution from HTEM data along with superior depth of investigation and sensitivity to 3D structures that is inherent in MT data. This paper describes the input data, modelling methods, and a detailed comparison of the results over a genuine blind geothermal system. The 3D joint inversion started from the result of a single-domain 3D inverse model of MT data only, then ran an initial joint-inversion employing a 2D HTEM forward solver only on lines perpendicular to structures. Following this result, a final, fully 3D inversion (MT + HTEM) was ran including all available HTEM lines. The final model exhibits improved near-surface resolution and minimizes near-surface artefacts in-between stations which are common when modelling MT data. All data and models are open-source and can be downloaded from the Geothermal Data Repository.
Topic: Geophysics