Correlation between Distributed Rayleigh Sensing (DRS) and Moisture Sensors as Indicators of Slope Instability

Summary This paper describes the verification of Distributed Rayleigh Sensing (DRS), traditionally associated with acoustic sensing, for monitoring low frequency activity on a slope prone to landslides that is used as the British Geological Survey’s landslide observatory at Hollin Hill, North Yorkshire, U.K. The observatory is monitored using a variety of geological survey instruments and provides a unique opportunity to compare measurement systems that have very different principles of operation. Previous studies of the slope have shown good correlation between the low frequency strain and temperature measured using the fibre with prior knowledge of the geology of the site and longer-term measurements made on more established geological survey instruments. This paper presents a more detailed comparison of measurements made on the DRS system over the winter of 2020/2021, with measurements of soil moisture content made on point sensors and estimates of ground movement measured using GPS marker posts. The DRS system is sensitive to multiple important indicators of slope instability and can monitor ground movement effectively. Areas of unstable ground can be clearly identified by the larger changes observed in the fibre output in those regions.