Controlled source EM array

• Subject Area: Geophysics and Geodesy
• Term: Funded in 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420426679

Exploration depths in excess of 1000 m with a good lateral coverage are becoming increasingly important for the exploration of mineral deposits, the exploration of deep groundwater reservoirs, and for geothermal exploration. These fields of application are of great societal relevance in the context of the scarcity of raw materials, the energy transformation and climate change. A main goal of the DFG-funded Heisenberg professorship "Deep electromagnetic exploration" is to develop the semi-airborne electromagnetic induction technique, which can achieve significantly higher penetration depths than classical airborne techniques. In this method, high-power transmitters are installed on the ground, and broad-band vector magnetic field receivers are towed over the footprint of the source with a helicopter. The magnetic fields image the eddy currents induced within the conducting earth and provide a means to reconstruct the subsurface electrical conductivity distribution by inversion. The airborne measurements are complemented with a sparse grid of ground-based electric and magnetic field recordings to improve the resolution. With this proposal, I ask for funding of an active EM array, consisting of a ground-based high-power transmitter and ground-based receivers. The instrument is required to conduct semi-airborne electromagnetics experiments. Prototypes of a helicopter-towed bird have been developed in a BMBF collaborative project and can be used for further measurements. In a mid-term perspective, we plan to use drones instead of helicopters. Because the drone technology is rapidly developing, it is not yet useful to purchase heavy drones with large payload now. For the development of drone geophysics, we will therefore rely on cheap drones with a maximum payload of 5 kg. Magnetometers and drones are available from the applicant. There is an overall need for further research and development, both for helicopter-and drone-borne measurements, until the method will be routinely applicable. Prerequisite for the implementation of these objectives is the availability of the requested active EM array. Particularly with respect to the high-power transmitter, trained personal is required for safe handling in the field. Therefore, transmitters cannot be requested from instrument pools without staff. For development tasks, and also for larger experiments, it is therefore mandatory to work with own devices and personnel.The requested instrument will be furthermore of great use in the other research fields of the working group. They will be particularly of use in magnetotelluric studies of the lithosphere. The experiments, which will be conducted with the instrument will provide the data needed for methodological developments as well as to address geological and geoscientific problems.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Aktives EM Array
• Instrumentation Group: 6620 Funkanlagen (außer Konferenz- und Saal-Sprechanlagen)
• Applicant Institution: Universität Münster
• Leader: Professor Dr. Michael Becken