Main geological and structural units of the study region. NPF: North Pyrenean Fault; NPFT: North Pyrenean Frontal Thrust; SPFT: South Pyrenean Frontal Thrust; SH: Sillon Houiller (sometimes also referred to as the “Toulouse Fault”); NPZ: North Pyrenean Zone; SPZ: South Pyrenean Zone. The triangles show the stations of the PYROPE (blue) and OROGEN transects (purple). The thick black lines show the position of the ECORS-Pyrénées and ECORS-Arzacq deep seismic sounding profiles, respectively located in the Central and Western Pyrénées (from Chevrot et al., 2018).