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EARTHQUAKE ›› 2025, Vol. 45 ›› Issue (2): 132-146.doi: 10.12196/j.issn.1000-3274.2025.02.009

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Pre-slip Movement and Earthquake Precursory Anomalies Observed at Linxia Seismic Station before the 2022 Luding MS6.8 Earthquake

XU Jian-sheng1, LI Li1, ZHANG Lei2, ZHANG Yu2, GAO Shuang-ling3   

  1. 1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
    2. Earthquake Administration of Gansu Province, Lanzhou 730000, China;
    3. Heilongjiang Earthquake Agency, Harbin 150000, China
  • Received:2024-04-01 Accepted:2024-10-18 Published:2025-09-05

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Abstract: Before the Luding MS6.8 earthquake in Sichuan Province on September 5, 2022, the borehole strain and water level meter of the Linxia seismic station in Gansu Province successively recorded a small pre-slip phase Xp0 from April 1, 2022, and four large-amplitude pre-slip phases Xp1—Xp4 were recorded “quasi-synchronously”. From April 20th, N large barometric pressure pulse phase Gp1 was recorded on the borehole barometer from August 10, 2022. More than 20 days before the earthquake, the diurnal variation of temperature in the Linxia seismic station was destroyed, and the temperature continued to be lower, accompanied by light rainfall. The air pressure difference between the borehole and the ground continues to increase. According to the above, more than 4 months before the earthquake, the surrounding blocks of the epicenter began a small pre-slip activity. The pre-slip activity squeezed the block where the Linxia seismic station located, resulting in the gas overflow in the cracks of the block, and excited the air pressure pulse with a large amplitude N times in the borehole. More than 20 days before the earthquake, there were four large- amplitude pre-slip activities in the block where the Linxia seismic station located. The pre-slip activity caused the gas to overflow in the cracks of the block, resulting in the continuous increase of the difference between the borehole pressure and the ground air pressure, and the fluctuation amplitude of the ground air pressure and the borehole air pressure also increased, and these meteorological anomalies did not return to normal until after the earthquake. The pre-slip activity of the block where the Linxia seismic station is located has a good correlation with earthquake precursory anomalies in time and space. Based on this, it is speculated that the pre-slip activity of the site where the Linxia seismic station is located before the earthquake may be the physical mechanism of earthquake precursory anomalies. Therefore, paying attention to abnormal signals such as pre-slip activities, changes in air temperature and air pressure, as well as changes in air pressure pulses and borehole pressure and ground pressure difference before the earthquake has a certain scientific significance for predicting future destructive earthquakes.

Key words: Pre-slip before earthquake, Earthquake precursory anomalies, Air pressure difference, Air pressure pulse phase, The 2022 Sichuan Luding MS6.8 earthquake

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