Previously hidden landslide processes revealed using distributed acoustic sensing with nanostrain-rate sensitivity

Abstract

Landslides can sometimes creep for decades before undergoing runaway acceleration and experiencing catastrophic failure. Observing and monitoring the evolution of strain in time and space is crucial to understand landslide processes, including the transition from slow to fast movement. However, the limited spatial or temporal resolution of existing landslide monitoring instrumentation limits the study of these processes. We present a method employing distributed acoustic sensing (DAS) strain data below 1 Hertz frequency over a three-day period of rainfall and quantify strain-rate changes at meter and sub-minute scales. The results reveal rainfall-triggered landslide processes, beginning with the onset of near-surface strain changes at the head scarp. Strain acceleration at a developing rupture zone, retrogression towards the scarp and flow-lobe activity is observed as the rainfall continues. The DAS-inferred processes with displacements of less than 0.5 mm are undetected using other landslide monitoring techniques. Our method illuminates landslide processes occurring with nanostrain-rate sensitivity at spatiotemporal resolution previously not possible.