Abstract
Groundwater is undoubtedly important for water security and eco-environmental protection, especially in areas that experience earthquakes. Analyzing the characteristics and variation of groundwater after an earthquake is significant to obtain a better understanding of the seismic risk and rational management of groundwater resources. This study investigated the hydrogeochemical characteristics of groundwater at the epicenter of the 2021 Biru M6.1 earthquake in central Tibet, southwest China, using 23 water samples. The results showed that: (1) the hydrochemical type, hydrogen and oxygen isotope ratios, and SiO2 concentrations of three hot spring water samples in the study area were significantly different from those of samples taken elsewhere, indicating that the hot spring water originates from deeper geothermal reservoirs and has undergone more distant migration and longer fractionation processes; (2) the geochemical characteristics of groundwater from some sampling sites in the epicentral area were apparently distinct from those of other shallow groundwater or surface water samples, suggesting that the groundwater environment in the epicentral area has been affected by the earthquake. Along with the macroscopic groundwater responses in the epicentral area after the earthquake, we investigated the influencing mechanisms of the earthquake on the regional groundwater environment. We conclude that a shorter distance from the epicenter to the seismogenic fault leads to a greater possibility of the generation of new fractures, which then induce macroscopic responses and chemical characteristic variations for groundwater.
Highlights
IntroductionHydrothermal activities are closely related to deep faults and active faults, and geothermal fluids can rapidly migrate along the fault channels [4,5]
The differences in hydrogen and oxygen isotope values suggest that the water bodies have different sources and have undergone different fractionation processes during migration
SiO2 content of the well water from w1, which suggest that the groundwater environment in the epicentral area has been affected by the earthquake
Summary
Hydrothermal activities are closely related to deep faults and active faults, and geothermal fluids can rapidly migrate along the fault channels [4,5]. In the processes of earthquake generation and occurrence, changes in the stress conditions of aquifers and mixing of deep and shallow fluids can cause variations in the chemical composition of groundwater in the fault zone and nearby areas [6,7,8,9,10]. We can capture possible earthquake precursor signals by analyzing the geochemical characteristics of groundwater associated with earthquakes, especially using the geochemical anomalies of geothermal water [11,12,13,14]
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