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TitleMagnetotelluric monitoring of impedance in an area of induced seismicity at Manic 3, Quebec / Enregistrement magnétotellurique de l'impédance dans une zone de sismicité induite à Manic 3, au Québec
AuthorKurtz, R D; Niblett, E R
SourceEarth Physics Branch, Geomagnetic Series no. 25, 1984, 38 pages, (Open Access)
PublisherEnergy, Mines and Resources Canada
Lang.English; French
Mediapaper; on-line; digital
File formatpdf
NTS22F/10; 22F/15
AreaRéservoir de Manic 3; Manic 3 Reservoir; rivière Manicouagan; Manicouagan River; Baie Comeau
Lat/Long WENS -69.0000 -68.5000 50.0000 49.5000
Subjectsgeophysics; reservoirs; water levels; water loading; seismicity; seismic risk; earthquakes; geophysical surveys; magnetotelluric surveys; telluric field; geomagnetism; geomagnetic fields; electrical resistivity; bedrock geology; Grenville Province; electrical impedance
Illustrationssketch maps; time series; tables; graphs; models; plots
Released1984 01 01; 2018 11 13
AbstractSeismic activity associated with the filling of the Manic 3 reservoir north of Baie Comeau, Quebec commenced in September 1975. Afler the magnilude 4.1 earthquake of October 23, 1975 three magnetotelluric (MT) stations were established in the area to monitor the electrical impedance of the earth and to relate any changes with the seismic activity. Two of the stations operated for over 1.5 years. During this time it was found that if any time dependence existed, it had the nature of a linear increase in the impedance of about 113 per year. There were no significant variations observed in the angle of polarization of the telluric fields nor were there any significant changes in the geomagnetic transfer functions. Afler the stations were installed, the seismic activity slowly decreased to very low levels. No large earthquake was predicted by the magnetolelluric results and none occurred.
The apparent resistivity curves along the major axis of anisotropy from the three stations are nearly the same as are the minor resistivity curves from two of the stations. They are similar to other MT curves obtained in the Grenville. The major axis of anisotropy is approximately north-south at all three stations. In addition, the transfer functions are nearly identical. The MT data are consistent with a substantial conducting layer at the base of the crust.