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Electrical conductivity structure of the crust on the Norwegian Continental Shelf from magnetotelluric data

Alternative title: Elektrisk konduktivitetstruktur av skorpen på norsk kontinentalsokkel fra magnetotelluriske data

Awarded: NOK 1.7 mill.

Project Number:


Project Period:

2019 - 2023

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Companies searching for oil and gas collect offshore electromagnetic data by deploying receivers on the seabed and a powerful source in the water. When the source is off or far away from the receiver, the natural background electromagnetic signal that contain MT data is recorded. Exploration companies do not usually use marine MT data because the method is too low-resolution to detect oil and gas reservoir and rather sense deeper in the crust, down to the Earth mantle! In this project, we analyze electromagnetic data from the industry and unleash the scientific potential of MT data on the NCS. The results are so far promising as high-quality MT data can be extracted for ~330 receivers laid on the seafloor of the Barents Sea. A detailed data analysis has shown that we can image the subsurface electrical down to 100 km, exceeding our initial expectations and allowing for a full reconstruction of the Earth brittle crust, the lithosphere, across the Barents Sea region. After in-depth data analysis, we explore the model space and find a 3D electrical model of the subsurface that can numerically replicate the observations. This is done with a 3D inversion code, an iterative process that converges to an optimal solution. We use seismic and potential field data to constrain the chosen 3D conductivity model with acoustic and density constraints. The project is a scientific journey to the depth of the Earth, leading to a realistic conductivity structure of the crust beneath the NCS emanating from three independent and complementary geophysical methods.

The structure and composition of the Earth’s crust is key to understanding the geological evolution of tectonic plates. Magnetotellurics (MT) is a large-scale geophysical method that image the electrical conductivity of the Earth’s crust using the natural variation of the electromagnetic field. For half century, a wealth of electromagnetic data have been acquired onshore for natural resource exploration but marine MT data remain scarce. In this project, we plan to process offshore electromagnetic data acquired by the exploration company in the North Atlantic margin and Barents Sea and extract MT data. Dimensionality analysis of the magnetotelluric impedance tensor should lead to a better understanding of the nature and distribution of telluric currents flowing in the crust. Through inversion and modelling studies, we will seek robust electrical conductivity models of the crust along selected area and transects that can reproduce the MT measurements. We will refine our conductivity model using seismic and potential field data. Using a multi-disciplinary modelling and interpretation approach, we aim at finding a crustal model that honors three independent geophysical measurement. The project will lead to a better understanding of magmatic and hydrothermal processes occurring in the Earth’s crust in a variety of geological settings of the NCS. The study will impact petroleum and mineral exploration by developing new concepts on deep crustal mechanisms and basin evolution.

Publications from Cristin

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