Review Iii, Submitted to Geophysical Journal International

We investigate the deformation induced by water pressure variations in hydrologicallyactive natural fractures, and recorded by tiltmeters and strainmeters. The deformation associated with a single fracture is derived using finite-element modeling (FEM). A range in fracture geometries is explored, first to highlight the sensitivity of each geometrical parameter to the deformation, and secondly to allow transfer to observation sites. Water level variations in the fracture are then derived from a hydrological model, driven by observed rainfall, and calibrated on fracture water flow measurements. The modeling results are explicitly applied to constrain the local hydrological contribution to observations with the 100-m long hydrostatic tiltmeter installed at Sainte-Croix-aux-Mines (France). Our study shows that well-founded physical modeling of local hydrological effect allows a substantial correction of records in observatories.