Two Different Layouts of Sensors of Four-gauge Borehole Strainmeter and Their Influence on Field Measurement

The four-gauge borehole strainmeters (FGBSs) used in mainland China include multiple instrument modes. The sensors in the four directions have two layout modes in the vertical direction: the same-plane mode and the different-plane mode. In this study, we obtained a large amount of site observation data and showed that the observation data collected using the two modes have certain differences. Through the establishment of a 3D finite element model and field measurement analysis, it was concluded that the inhomogeneity of the coupling cement at different levels influenced the observations of the sensors in the different-plane mode, and the observation data were less self-consistent than those for instruments with sensors in the same-plane mode. The self-consistent characteristics of the FGBS provide an algorithm for AI-based seismic research. Comprehensive analysis showed that for the four sensors of the FGBS, the same-plane layout was the optimal choice.