Investigation of the Rainfall Effect on Strain Observed by Extensometers at the Jixian Seismostation in China

Strain data at Jixian seismostation have been exhibiting long term extensional trend since installation in 2018, and with clear annual variation and accelerated change during heavy rainfall. We categorize the rainfall effect into short-term and long-term effect. Strain changes induced by heavy rainfall in short term are diverse and complex, with 2 or 3 types of responses in the same direction. The extensional trend of strain in long term is caused by a continuous effect of water storage accumulation at Jixian seismostation, as we find from linear regression between total rainfall and strain long-term variation. Loading effect and pore pressure change of the aquifer cause strain changing rapidly. The continuous accumulated waterstorage changed leads to the permanent and small extensional deformation. Such findings provide insight into the influence of rainfall on deformation and seismic precursor anomaly.