Notable Annual Thermoelastic Strain in Vault-housed Extensometers: A Typical Case from the Kuancheng Geodynamic Observatory, North China

Clarifying the physical mechanisms underlying near-surface annual deformation remains a formidable challenge in crustal dynamics research. In the past few decades, quite a few extensometric observatories exhibit notable and regular annual variations in strain signals in mainland China. However, the geodynamic investigations on these prevalent but intriguing strain signals remain rare till now. Since outdoor air temperature is a key factor contributing to annual deformation of the Earth’s crust, this work therefore quantitatively elucidates the mechanism via which annual atmospheric temperature variation influences the NS and EW components of strain by analyzing data observed at the Kuancheng Geodynamic Observatory, North China, with an elastic half-space model covered by elastically thin unconsolidated layer. According to the modeled results, annual variation of atmospheric temperature with an amplitude of 16.84 ℃ is sufficient to produce a thermoelastic strain of 10 ^− 7 magnitude inside the mountain at a depth of 30 m. Besides, both the modeled amplitudes and phases align closely with the observed strain signals, suggesting that the annual variations of the strain observed at the Kuancheng Geodynamic Observatory mainly originate from annual variations of atmospheric temperature. The method of geodynamic diagnostics used here and obtained findings not only contribute to the quantitative interpretation of the mechanism underlying annual variations in vault-housed extensometers in mainland China but also advance our understanding of the temperature-induced deformation processes within the near-surface crustal layer.