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EARTHQUAKE ›› 2025, Vol. 45 ›› Issue (2): 1-20.doi: 10.12196/j.issn.1000-3274.2025.02.001

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Comprehensive Evaluation of Groundwater Burial Types of Seismic Observation Wells in the Longmenshan Fault Zone and Their Relationship with Earthquakes

RUI Xue-lian1, YANG Yao1, ZHANG Wen-xu2, RAN Xi-yang1, XUE Qiao-wen3, HE Chang1, WU Hao1   

  1. 1. Sichuan Earthquake Administration, Chengdu 610041, China;
    2. Institute of Disaster Prevention, Sanhe 065201, China;
    3. Department of Emergency Management of Sichuan Province, Chengdu 610047, China
  • Received:2024-04-08 Accepted:2024-08-15 Published:2025-09-05

Abstract: Based on the digital data of water level and air pressure of nine seismic observation wells in the Longmenshan fault zone, we used the spectrum analysis method, the step response function method of well water level to air pressure, the phase advance or lag method of tidal wave group, and the water-rock equilibrium analysis to comprehensively evaluate the groundwater types of each well. Based on the evaluation results, we selected seven observation wells with good tide response to analyze the time series characteristics of the M2 tidal factor and phase lag of groundwater levels, and to study their relationship with earthquakes. The results indicate that only the groundwater of the DY-08 well is confined water, while the rest are mixed water. Among the nine observation wells, the confining capacity of DY-08 well is the best, then is the JY-10 well. Before the strong earthquakes in western Sichuan Province and nearby areas, there are obvious short-term anomalies with rapid rises or falls in the tidal factor and phase difference of well water levels. These rapid changes before the earthquakes reflect the changes in stress and strain in the aquifer of the observation wells during the earthquake gestation process. Considering the geological structure and spatial distribution of the observation wells, we conclude that the short-term anomalies of the tidal factor and phase lag of groundwater levels starting in March 2022 correspond to the 2022 Lushan M6.1 earthquake rather than the 2022 Ma’erkang M6.0 earthquake swarm. The conclusion of this study provides significant references for evaluating the water level observation quality of seismic observation wells, determining the reliability of anomalies, and researching and judging regional seismic trends in the future.

Key words: Well water level, Groundwater types, Earthquake, Tidal response, Longmenshan fault zone

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