Induced polarization of volcanic rocks. 4. Large-scale induced polarization imaging

SUMMARY Thanks to the emergence of new technologies developed with goal performing large-scale galvanometric induced polarization surveys and thanks a better understanding underlying physics polarization, this geophysical method can now be applied in field volcanology geothermal resources assessment. A approach is here for directly inverting primary secondary electric fields recorded at set independent stations when injecting current. The use measure electrical improves quality data by reducing capacitive coupling effects inherent systems based on long cables. It avoids issues associated using same electrodes both current injection voltage measurements negative apparent resistivity chargeability values. With such acquisitions, we perform true 3-D areas characterized complex topography as volcanoes. numerical scheme returns output conductivity fields. implemented methodology presents several advantages. first types stations, example intensity, that are from local geometrical station parameters electrode spacing dipole orientation. second advantage lies suitability proposed applications since matrix-free does not require assembly Jacobian matrices. third concerns possibility inversion geometries through consistent finite element unstructured meshes combination algebraic multigrid preconditioning regularization solution forward adjoint problems. computation sensitivity maps also real asset survey design. After validating our benchmark synthetic case study, test it mimic conditions volcanic environment rough topography. Our tests demonstrate high potential especially deep (3 km) imagining internal structure volcanoes, which turn could improve hydrothermal allow monitoring active volcanoes risk collapse.