Theoretical and earthquake-induced groundwater chemistry changes: A perspective

To minimize the loss of life caused by earthquakes, it is crucial to have early warning tools that provide sufficient warning time. Although various methods are available, their accuracy is uncertain. This review explores alternative indicators related to hydrogeochemical anomalies that appear before earthquakes, which could potentially offer earlier warnings. It presents a theoretical basis for ionic and molecular changes initiated by the generation of hydroxyl radicals (•OH) and hydrogen peroxide (H₂O₂) in groundwater before an earthquake. The review analyses 32 earthquake events by measuring ionic anomalies through standard reduction potential. The study also identifies significant pre-seismic erosional activity in minerals exposed to hydrogen peroxide. Additionally, the oxidation of organic compounds is shown to predict notable geochemical changes. The changes in the groundwater chemistry can also be validated by examining simultaneous microbial/ zooplankton responses. The findings suggest that the ionic, mineral, organic, and microbiological changes triggered by hydroxyl radicals and hydrogen peroxide could serve as a multi-parametric earthquake early-warning system. Implementation of such a system could improve the accuracy and timeliness of earthquake warning systems potentially reducing the associated risks and damages.