Abstract: This paper introduced the domestic and foreign research progress on borehole strain, explored the influencing factors of borehole strain, and provided an introduction and summary of borehole strain data identification, reliability, and analysis methods. The study analyzed the earthquake precursor anomalies, co-seismic responses, and earthquake models based on borehole strain data, finding that current borehole strain observations are insufficient to meet all seismic observation needs, with seismic precursor observations still in need of confirmation and verification. It is recommended to establish a comprehensive subsurface monitoring system and integrating other observation methods to address the shortcomings of borehole strain observations, thereby better understanding the patterns and characteristics of borehole strain for future seismic monitoring reference purposes.

Key words: Borehole strain gauger, Borehole strain observation, Crustal deformation