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Time-lapse surface wave monitoring of permafrost thaw using distributed acoustic sensing and a permanent automated seismic source



We present preliminary results from an intermediate scale field experiment exploring the seismic response of dynamic permafrost thaw generated by active heating. The focus of our project was to evaluate the utility of surface wave monitoring to detect precursors to thaw-induced subsidence, a common geotechnical hazard in polar regions. In this study, we present results from timelapse surface wave measurements conducted over the duration of the thaw experiment. The unique aspect of the experiment was the combination of a semi-permanent surface orbital vibrator (SOV) source and distributed acoustic sensing to measure variations in surface wave propagation. The SOV, energized for 22 sweeps every night, was deployed for approximately 2 months, collecting 60 daily surveys. Large temporal variations in surface wave velocity, as well as spectral characteristics were observed. After examination of precipitation and soil moisture data, such changes were convincingly linked to rainfall events. A cross-equalization approach was developed to assist in removing this effect; after processing, a decreasing trend in shear wave velocity appears to remain, potentially a seismic signature of the controlled permafrost thaw process.

Presentation Date: Monday, September 25, 2017

Start Time: 4:20 PM

Location: 370C

Presentation Type: ORAL