In-situ monitoring of rock slope destabilization with ambient seismic noise interferometry in southwest China

The damage evolving on rock slopes, including unstable mass failure events, is expected to be associated with a rigidity loss of geomaterials. Therefore, velocity changes (dv/v) inferred from ambient noise interferometry allow remotely assessing the damage state of the slope. However, the time scale and amplitude of the dv/v evolution associated with the slope destabilizations are not well known, and their detection and characterization require both high precision and high temporal resolution in dv/v. We herein report an in-situ one-year monitoring of the dv/v on the slow-moving Pubugou rock slope with a high temporal resolution up to 20-min by using two seismic stations in the mountainous region of Sichuan, China, where the slope is affected by both earthquakes and rainfall. The results confirm the feasibility of (1) detecting a possible precursor dv/v drop (-0.5%) similar to 40 min before a slope destabilization; (2) characterizing the dv/v caused by the superimposed effects of moderate earthquakes and rainfall; and (3) quantifying the daily dv/v fluctuations of the slope caused by the environmental thermal forcing through thermoelastic effects. In addition, the measurement error and the detectable depth resolution of the dv/v are also addressed in this study. Finally, we suggest the high-resolution technique as a complementary means to be used for operational rock slope damage surveillance in the future.