Intermediate tectonic pattern and hydrodynamic process deduced from audiomagnetotelluric investigations on the volcanic island of Mayotte (Comores Archipelago)

Audiomagnetotelluric soundings were carried out on the volcanic island of Mayotte (Comores Archipelago). The field method and data are described and discussed. All the sounding cross sections show coherent curves with a high conductive layer between 100 and 200 m. depth. This layer is considered to be a fluctuating water table zone correlated to yearly climatic changes under tropical weathering processes. Dipping and sudden level variations are linked to tectonic volcanic features and are the visualization of a block faulting system of the primitive basaltic shield, a consequence of a distensive phase possibly connected with the collapse of the western flank of the volcano. Piano-key panels are the typical sub-surface style and the guide-line for any water prospection on the volcano and the activity of the island water transfer system.