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Summary Although many are suspected from seismic observations, few and far between Permo-Carboniferous (PC) troughs at the top of the Variscian basement in Switzerland are confirmed by wells. The well-known and geothermally relevant Northern Swiss trough with its top in a depth of about 1.5 km has been first identified in its spatial extension by gravity measurements revealing its smaller density with respect to the crystalline basement. Further south, towards the Alps, paleo-graben structures are expected to occur with a top depth down to about 5 km following the deepening of the top crystalline basement. A sensitivity study using Butterworth filter of different wavelengths applied to realistic 2D and 3D geological models was conducted in order to understand the gravity variation with increasing depth of the top of the troughs. It reveals high potential in the delimitation of the PC troughs at significant depth as well as in tracing their vertical geometry using the different wavelengths. Application on the real data confirms the interpretation of negative anomalies in terms of PC troughs.