Detection of shallow sedimentary structure of Yigong Lake in Tibetan Plateau using distributed acoustic sensing

Abstract

The Tibetan Plateau is poorly instrumented with conventional geophysical sensors due to its harsh natural condition. Densely sampled seismic data both in time and space are rarely available for environmental seismology study and natural hazards monitoring. The emerging distributed acoustic sensing (DAS) technology provides the possibility for continuous measurements of the dynamic strain by repurposing the fiber optical cable as a dense seismic array to bridge observational gaps. We deployed two survey lines with armored fiber optical cables in the Yigong Lake area, Southeastern Tibetan Plateau to record ambient noise for a week. The DAS interrogator is specialized by using a 12V-DC battery for power supply due to the power limitation in the field. We show the analysis of four-hour data of a 0.66km-long fiber optical cable using seismic interferometry of ambient noise and multichannel analysis of surface wave. We get a 2D shear-wave velocity profile along the cable and reveal that the sedimentary thickness of the Yigong Lake area is larger than 80m. The current research demonstrates the potential of DAS for dynamic monitoring of the geologic evolution of lakes and rivers in the Tibetan Plateau.