Postseismic mountain aquifer leakage drives multi-annual forearc basin recharge in the Atacama Desert

Abstract

In response to a 7.8 Mwb earthquake in June 2005 in the hyper-arid Atacama Desert, postseismic mountain aquifer leakage was triggered at several sites. By creating data-driven models for selected water level time series, previously unconsidered processes of postseismic mountain aquifer leakage are analysed. Post-event lag-time changes imply that the hydraulic conductivity of the assessed mountain aquifer doubled in response to the earthquake, initiating a multi-year period of augmented mountain-block recharge to the forearc basin. An estimate of the magnitude of mountain water releases after June 2005 suggests that released storage water exceeded the recharge provided by a 100-year rainfall event fourfold. During an observation period of 43 years two such events likely occurred in the study area. The frequency of postseismic mountain aquifer leakage, its contribution to draining eventual head decays in the Atacama Desert as well as its importance for forearc basin water budgets are discussed.