For the first time, the passive seismic instrumentation of an entire glacier close to the flow line was realized by researchers from ETH Zürich (Prof. Dr. A. Fichtner & Prof. Dr. F. Walter, SNF Spark grant): State of the art DAS (distributed acoustic sensing) technology paved the ground to acquire seismic data with a fiber-optic cable over an extent of 9 km following a zig-zag patternand covering Rhônegletscher (Swiss Alps) from its accumulation to its ablation zone.
Rhônegletscher is a temperate and well accessible glacier located in the Swiss Alps, with a length of 9 km (~15.5 km2 total extension) and an average surface slope of 10°, ranging in elevation between 3600 to 2200 m above sea level (a.s.l.) (GLAMOS, 2020). Data on Rhônegletscher were collected using distributed acoustic sensing (DAS) technology (Walter et al., 2020; Hudson et al., 2020). DAS measurements are based on an interrogator emitting a sequence of „outgoing“ laser pulses into an optical fiber. The light experiences scattering at inhomogeneities along the cable and is recorded as an „incoming“ pulse back at the interrogator. Phase shifts of the backscattered light provide a highly sampled time series of tiny cable strains, such as those induced by passing seismic signals. Seismic recordings can thus be obtained every few meters along the cable offering the possibility to record incident seismic waves with frequency sensitivity ranging from millihertz to kilohertz (Farhadiroushan et al., 2009, Parker et al., 2014).
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