3D geological modelling using geological / geotechnical and AEM data

• Main Authors: Deparis, Jacques, Vittecoq, Benoit, Jaouen, Timothée, Lacquement, Frédéric, Perrin, José, Martelet, Guillaume
• Other Authors: Bureau de Recherches Géologiques et Minières (BRGM), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2013
• Subjects: Electromagnetism; 3D modelling; Mayotte; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDE.MCG]Environmental Sciences/Global Changes; Young Island
• Online Access: https://brgm.hal.science/hal-00873252; https://brgm.hal.science/hal-00873252/document; https://brgm.hal.science/hal-00873252/file/Deparis_etal_3D_Geological_modelling_AEM.pdf

Understanding the hydrogeological functioning of volcanic island is essential for an adapted management of water resource and for a better supply to population, particularly in those who have seen their population increase in years. Nevertheless, geological, hydrological or hydrogeological data are often very scarce, and appropriate approach have to be found in order to improve the hydrogeological functioning of these islands. Groundwater resource is closely correlated with the permeability of rocks, and, in basaltic volcanic islands, permeability is usually considered to be negatively correlated with age formations. Younger lavas have higher permeability than older one's often highly weathered (Custodio et al., 1988). Existing hydrogeological models of basaltic volcanic islands describe large-scale systems at the volcano or island scale, and two end models have been described. The Hawaiian model (Meinzer, 1930) considers a low-lying basal aquifer linked to inland dike-impounded and perched aquifers overlying impervious layers and/or confined by dykes (Tabasaki and Mink, 1983). The Canary Islands model (Custodio, 1975; Custodio et al., 1988) considers a continuous and isotropic basal aquifer, and a decrease of hydraulic conductivity with the age of the volcanic rocks. Nevertheless, those models are consistent with Young Island (< 5 Ma) and seem not fully appropriate for older island such as Mayotte Island. Mayotte Island is a small French overseas territory of the Comoros archipelago in the Indian Ocean. Its population has quickly increased during the last decades and has been multiplied by four in less than 30 years. The island is now very densely populated with more than 500 inhabitants per square kilometer. Water needs are thus substantial. Surface water resource is very strongly solicited, and too dry seasons can lead to critical situations. Nevertheless, its hydrogeological functioning is not well known, and understanding the hydrogeological functioning of the island is thus essential for an adapted ...