Surface deformation monitoring at geothermal exploitation: a review and case study of Soultz-sous-Forêts and Rittershoffen sites in the Rhine Graben, France

Abstract

The monitoring of surface deformation at geothermal exploitation sites can be performed using terrestrial and/or space techniques. Terrestrial techniques such as gravimetry and leveling provides accurate measurements but at few specific points (e.g. Ferhat et al 2015, 2016; Hinderer et al 2015, 2016). InSAR provides LOS (Line of Sight) temporal variations not directly or easily convertible into horizontal and vertical deformations. We present a review of surface deformation measured at several geothermal exploitation sites. This deformation were in some cases expected, but also accidental. It is shown the importance of terrestrial measurements such as leveling or GNSS stations for capturing correctly surface deformation, and in particular vertical surface deformation. The two geothermal exploitation sites of Soultz-sous-Forêts and Rittershoffen, located in the Rhine Graben, France are presented. At these sites, repetitions of relative gravimetric and levelling measurements are annually performed on large scale (few km).