Geochemical Anomalies in Groundwater as Precursors to Earthquakes in Azerbaijan

This study presents the results of long-term hydrogeochemical and radiogeochemical monitoring in Azerbaijan’s seismogenic zones, focusing on the relationship between groundwater composition and seismic activity. Data were collected from key observation wells, including Shamakhi No. 8 and Chukhuryurd No. 49, where fluctuations in major ion concentrations, oxidation-reduction potential, pH, and dissolved gases were systematically recorded. The study analyzes two significant seismic events – the Baku earthquake (November 25, 2000; M = 6.8; h = 13 km) and the Shamakhi earthquake (February 5, 2019; M = 5.3; h = 8 km) – which serve as case studies demonstrating the predictive value of hydrogeochemical anomalies in earthquake forecasting. Prior to both earthquakes, distinct geochemical changes were observed in the groundwater. These included sharp increases in sulfate (SO₄²⁻), iron (Fe²⁺, Fe³⁺), and carbonate (CO₃²⁻) concentrations, along with significant depletion of sodium (Na⁺), potassium (K⁺), and halogen ions (Cl⁻, Br⁻, I⁻). Additionally, variations in pH and oxidation-reduction potential were detected, reflecting shifts in subsurface stress conditions. Water level fluctuations were recorded, often accompanied by noticeable color changes, such as water blackening shortly before seismic activity. Another key finding was a dramatic increase in helium (He) concentrations – rising nearly tenfold – highlighting its sensitivity as a precursor to tectonic movements. These patterns were consistently reproducible, reinforcing their significance as seismic indicators. The study underscores the importance of integrating hydrogeochemical and radiogeochemical monitoring into earthquake forecasting models. Notably, alpha radiation fluctuations and shifts in oxidation-reduction potential provided additional insight into subsurface stress changes. Expanding monitoring networks, utilizing real-time data analytics, and incorporating these geochemical signals into early-warning systems could enhance earthquake preparedness in Azerbaijan’s seismically active regions, mitigating risks and improving response strategies. Strengthening interdisciplinary collaboration among geoscientists, seismologists, and local authorities can further optimize hazard assessment and response mechanisms, ultimately reducing the impact of destructive earthquakes on communities and infrastructure.