Quantification of the Impact of temperature variation on tiltmeter recordings for ground deformation monitoring

Geothermal energy, driven largely by the push towards achieving net-zero emissions, has garnered increasing interest in the past decades for electricity generation. Geothermal-related activities, as any other activity for energy projects that utilise the subsurface, could induce subtle deformations on the near-surface. Tiltmeters is a technology capable to detect submillimetre ground deformations but can be significantly affected by ambient temperature variations. This effect can mask potential minute deformation signals. The effect of ambient temperature variations on tiltmeter recordings still lacks systematic understanding due to the absence of precise monitoring data and appropriate interpretation guidelines. In this study we analysed continuous tiltmeter recordings for a full year period and quantified the close correlation between the ambient temperature and ground displacement in both east-west (EW) and north-south (NS) directions. This close relationship has also been suggested by their wavelet coherence (WTC) results with only small time-lag observed. Overall, appropriate recognition of temperature-related ground motions can benefit the understanding of shallow crust and promote the establishment of baseline for future geothermal-related practices.