Résumé
In the face of growing challenges regarding the security of water supply, deep karstic carbonate aquifers represent a strategic resource. However, exploring them remains complex due to their high degree of heterogeneity, depth, and overlying formations that are sometimes poorly understood. In this context, geophysical methods offer promising prospects for imaging these hard-to-access systems, provided they are strategically integrated.A multi-scale, multi-method geophysical approach was tested in order to constrain the Jurassic reservoir beneath the cover rocks of the Pays de l’Or region in southern France (Hérault). This approach combines geophysical mapping using gravity and passive seismic (H/V) surveys to characterise geological structures with 2D imaging using high-resolution seismic reflection (SRHR) and electrical resistivity tomography (ERT) to study the overlying formations and their hydrogeological characteristics in more detail, down to a depth of 300 metres. This approach enabled the physical signatures obtained to be compared, and the results demonstrate that the methods complement each other well. Jointly analysing the data enabled us to refine the structural model, constrain the nature and geometry of surface and deep formations, identify structural, erosional or weathering discontinuities affecting them (e.g. fracturing), and detect potentially karstified zones. Although technically demanding, multi-method approaches enable the formulation of robust geological and hydrogeological hypotheses and can effectively guide future investigations (e.g. drilling, hydrogeological monitoring). Therefore, they represent a promising tool for improving our understanding of the critical zone in a karst context.