Changes in permeability caused by dynamic stresses in fractured sandstone

Shaking-induced changes in permeability have been invoked to explain a wide range of hydrologic responses to earthquakes. We measure the evolution of permeability in fractured sandstone in response to repeated shaking under undrained conditions. The frequency and amplitude of the imposed shaking are similar to those from earthquakes at distances of similar to a fault length from the ruptured fault. To assess the role of mobile particles, we also add silt-sized particles to the fractures. We find that, in general, permeability decreases after shaking. The samples with added particles show larger changes in permeability. Shaking-induced transport of particles to block narrow fracture apertures can explain some of the observations. We also find that decreases in permeability are often accompanied by a contraction of sample indicating that fracture apertures sometimes decrease, presumably by mobilizing particles and removing asperities that hold fractures open. Citation: Liu, W., and M. Manga (2009), Changes in permeability caused by dynamic stresses in fractured sandstone, Geophys. Res. Lett., 36, L20307, doi: 10.1029/2009GL039852.