Abstract
The mantle electrical conductivity-depth profile of the Niger delta region in Nigeria has been determined using solar quiet day ionospheric current (Sq). The magnetometer data obtained in 2010 from geomagnetic stations installed in Lagos by magnetic dataset (MAGDAS) in 2008 and data from magnetometers installed in some parts of Niger delta by Center for Basic Space Science, University of Nigeria, Nsukka, were employed in this study. Gauss spherical harmonic analysis (SHA) method was used to separate the internal and external field contributions to Sq current system. The result depicted that the conductivity profile rose steadily from about 0.032 S/m at a depth of 89 km to 0.041 S/m at 100 km and 0.09 S/m at 221 km. This high conductivity region agreed with the global seismic low velocity region, the asthenosphere. The conductivity profile continued increasing downward until it got to 0.157 S/m at a depth of about 373 km (close to the base of upper mantle), 0.201 S/m at 784 km and reached 0.243 S/m at a depth of 1179 km at the lower mantle.
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Acknowledgements
The authors are grateful to MAGDAS, Japan, for the data used in this work; Dan Okoh of Centre for Basic Space Science, University of Nigeria, Nsukka and Jonas Agbo of the Department of Physics and Astronomy, University of Nigeria, Nsukka, for their valuable contributions. They also thank immensely the reviewers for their thorough work and the Associate Editor (Dr Pawan Dewangan) for his meticulous and encouraging work.
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Obiora, D.N., Okeke, F.N., Yumoto, K. et al. Mantle electrical conductivity profile of Niger delta region. J Earth Syst Sci 123, 827–835 (2014). https://doi.org/10.1007/s12040-014-0425-0
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DOI: https://doi.org/10.1007/s12040-014-0425-0