Analysis of variation characteristics of Gaotai borehole strain observation data

Analyzing the observational data variation from the Gaotai borehole strain instrument showed that the YRY-4 borehole inclinometer has provided continuous, stable, and reliable data over the last nearly 18 years of operation. These data accurately and objectively reflect the changes in crustal stress in the Gaotai area, providing precise and trustworthy data support for geophysical and earthquake prediction research. The observational results indicate that the principal azimuth angle and principal strain of the Gaotai borehole strain exhibit a trend of tensile state. This is particularly with the tectonic principal strain showing a long-term tensile trend from west to east. The maximum and minimum principal strains of the Gaotai borehole strain also demonstrate a certain annual variation pattern, characterized by periodic expansive and contractile changes.