Integrated geophysical monitoring of active geothermal systems in the Mediterranean: a review of seismic, magnetotelluric, CSAMT and near-surface EM/GPR methods

Active geothermal systems in the Mediterranean occur in a tectonically diverse belt shaped by subduction, slab rollback, back-arc extension, active faulting and Quaternary volcanism. These settings offer an excellent natural laboratory for integrated geophysical monitoring because the same systems combine deep heat sources, structurally controlled permeability, clay alteration, complex fluid phase changes and strong near-surface heterogeneity. This review evaluates the complementary roles of seismic methods, magnetotelluric and controlled-source audiomagnetotelluric imaging, self-potential, transient electromagnetic methods and ground-penetrating radar for the exploration and monitoring of Mediterranean geothermal fields. A new practical synthesis case study for Campi Flegrei is included to move beyond a purely narrative review: it compares method sensitivity, depth of investigation, uncertainty sources and decision value using original review-level plots and a transparent scoring matrix. Representative examples from Milos, Nisyros, Santorini, Etna, Ischia and western Anatolia are used to test transferability across different geothermal play types. The review concludes that future progress in Mediterranean geothermal characterization will depend less on any single technique than on uncertainty-aware integration of geophysical, geological, geochemical and geodetic information, supported by explicit reporting of resolution and alternative interpretations.