Location and geological map of the gas storage reservoir. (a) Regional setting in Southwestern France (Map data: Google, Landsat/Copernicus, SIO, NOAA, US Navy, NGA, GEBCO) that contains modified Copernicus Sentinel data (2016) and the 25 km cell of the EASE equal-area grid used by the SMOS satellite alongside the Prime Meridian (black square). (b) Simplified superficial geology of the studied zone modified from the BRGM geological map of France at the 1:50,000 scale showing the reservoir isobaths (red lines), the ~25 km SMOS grid cell and 1931 measurement points using SqueeSAR® method including 1303 Persistent Scatterer PS (black circle) and 628 Distributed Scatterer DS (black triangle). Also shown are three selected zones (white empty rectangle) with the relative locations of the Lussagnet (L1) and Izaute (I1) gas exploitation wells (red filled square) and the Lussagnet/Izaute monitoring wells (red empty square). (c) Location of a reference zone (black rectangle) with four PS (black circle) and six DS (black triangle) and the Reference Point (yellow star) around the 790 m/NGF isobaths and outside the Tortonian clay surface layer. (d) Location of the Lussagnet exploitation zone with the selection of four PS and four DS inside the 452 m/NGF isobath and the location of two monitoring wells (L2 and L3). Also shown are the locations of shallow wells (black square) that are geological logs extracted from the BRGM subsurface database (BSS). (e) Location of the Izaute exploitation zone with eleven PS and three DS inside the 452 m/NGF isobaths, four monitoring wells (I2, I3, I4, I5) and three BSS shallow wells. Maps b-e were created using QGIS. QGIS Development Team, 2016. QGIS Geographic Information System (Version 2.18.0). Open Source Geospatial Foundation. http://qgis.org.