Evidence of fractures from the image of the subsurface in the Akonolinga-Ayos area (Cameroon) by combining the Classical and the Bostick approaches in the interpretation of audio-magnetotelluric data

A. Meying¹ , T. Ndougsa-Mbarga²* and E. Manguelle-Dicoum¹

¹Departement of physics, Faculty of science, University of Yaoundé I, P.O. Box 812 Yaoundé Cameroon.

²Departement of physics, Advanced Teacher’s Training College, University of Yaoundé I, P.O. Box 47 Yaoundé Cameroon.

*Corresponding author. E -mail: tndougsa@yahoo.fr

Accepted 24 September, 2009

   Abstract

Exploitation of audio-magnetotelluric data has been realised by combining the classical and Bostick approaches with the objective to determine the structuring of layers in the Akonolinga-Ayos subsurface area. The work has been devoted to the processing and interpretation of audio-magnetolluric data of two profiles respectively Akonolinga-Mengueme and Mbang-Metol which are approximately running N-S and have nine stations of measurement each over a distance of 35 - 40 km. These two profiles cover a length of 70 km in the E-W direction. Different representations of data have been used and have shown interesting results. The geoelectrical sections derived from these two approaches show the topography of the subsurface with many discontinuities. This topography presents a major deep-seated fault passing through Ngultangan and Olembe and another between Ebale and Envong which passes through Awo’o, both directed E-W. Different geological sections have also been proposed. A discussion of results issued from these two approaches show that the Bostick approach brings out more details in the structuring of layers than the classical approach. The combination of the two approaches is necessary for a better interpretation of audio-magnetolluric data as we have realized during this study.

Key words: Audio-magnetotelluric soundings, classical and Bostick approaches, interpretation, fault.