Reservoir-induced seismicity associated with the Itoiz Reservoir, Spain: A case study

Abstract

Reservoir-induced seismicity was observed in 2004 after the impoundment of the Itoiz Reservoir in the central-western Pyrenees, Spain. Subsequent annual filling cycles were accompanied by large epicentral growth in the northern part of the Jaca-Pamplona basin. Based on the evaluation of the available geohydrologic data, we suggest that the seismicity is associated with the diffusion of increased pore pressures along the carbonate megabreccia systems of the Early to Middle Eocene age Hecho Group. Assuming 1-D pore-pressure diffusion from the Itoiz Reservoir, we estimate that excess pore pressures of ∼100-500 kPa are adequate to induce M ≥ 3.0 earthquakes in this geological terrane. The results of this study have potential applicability in regions where reservoirs are built over karst terranes. © 2010 The Authors Journal compilation © 2010 RAS.