Seismic instruments: article

Energy-4 generator for monitoring seismically active zones and electromagnetic sounding of the Earth's crust; the experience of application in the Kovdor-2015 experiment
V. Kolobov1
M. Barannik1
B. Efimov1
A. Zhamaletdinov2,3,1
A. Shevtsov3
Y. Kopytenko4
1 Centre for Physical and Technological Problems of Energy in Northern Areas of the Kola Science Center of RAS, Apatity, Russia
2 St.-Petersburg Filial of Institute of Magnetism, Ionosphere and Radio Wave Propagation of the RAS, St.-Petersburg, Russia
3 Geological institute of the Kola Science Center of RAS, Apatity, Russia
4 St.-Petersburg Filial of Institute of Magnetism, Ionosphere and Radio Wave Propagation of the RAS, St.-Petersburg, Russia
Journal: Seismic instruments
Tome: 53
Number: 3
Year: 2017
Pages: 55-73
UDK: 621.314:(550.34+550.837)
DOI: 10.21455/si2017.3-5.
Keywords: Energy-4 generator, audio frequency range, power transformer, PWM inverter, frequency sounding, Baltic shield, seismically active zone, seismogenic layer, conductive layer, DD layer
Аnnotation: The 29 kW Energy-4 generator is designed for electromagnetic sounding of the upper crust and monitoring of seismically active regions. The generator operates in the audio frequency range from 4 Hz to 2 kHz. The maximum output voltage of the generator is 1200 V. Energy-4 generator is mounted on board a ZIL-131 truck and powered by two 14.5 kW direct-current generators. The main units of the generator are IGBT-based PWM inverter and step-up transformer. Electric circuit and construction of the generator are described in the article. Full-scale testing of the Energу-4 generator was performed within the framework of Kovdor-2015 experiment. For this purpose, multibeam frequency soundings at distances of 25 and 50 km between source and receiver were carried out on the area of 200´100 km. The area belongs to the territory of Archaean basement of the Baltic Shield. The Kovdor-2015 experiment results showed the existence of an intermediate conductive layer in the upper part of the Earth's crust at depths of from 2-3 to 5-9 kilometers with longitudinal conductivity from tenths of a siemens to a few siemens. The nature of the layer is explained by dilatancy-diffusion phenomena. It was called the DD layer. The studied DD layer is considered as a seismoactive element of the brittle upper Earth's crust of 10-15 km thickness.