Catchment‐Scale Architecture of the Deep Critical Zone Revealed by Seismic Imaging

Weathering and erosion processes are crucial to Critical Zone (CZ) evolution, landscape formation and availability of natural resources. Although many of these processes take place in the deep CZ (similar to 10-100 m), direct information about its architecture remain scarce. Near-surface geophysics offers a cost-effective and minimally intrusive alternative to drilling that provides information about the physical properties of the CZ. We propose a novel workflow combining seismic measurements, petrophysical modelling and geostatistical analysis to characterize the architecture of the deep CZ at the catchment scale, on the volcanic tropical island of Basse-Terre (Guadeloupe, France). With this original workflow, we are for the first time able to jointly produce maps of the water table and the weathering front across an entire catchment, by means of a single geophysical method. This integrated view of the CZ highlights complex weathering patterns that call for going beyond "simple" hillslope CZ models.