Downhole distributed acoustic seismic profiling at Skytrain Ice Rise, West Antarctica

• Published in: The Cryosphere
• Main Authors: A. M. Brisbourne, M. Kendall, S.-K. Kufner, T. S. Hudson, A. M. Smith
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Antarctic; Skytrain Ice Rise; Weddell; Weddell Sea; West Antarctica; Antarc*; Antarctica; Ice Sheet; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-15-3443-2021; https://doaj.org/article/a64b50a8d88247298799fb2d92f83352

Antarctic ice sheet history is imprinted in the structure and fabric of the ice column. At ice rises, the signature of ice flow history is preserved due to the low strain rates inherent at these independent ice flow centres. We present results from a distributed acoustic sensing (DAS) experiment at Skytrain Ice Rise in the Weddell Sea sector of West Antarctica, aimed at delineating the englacial fabric to improve our understanding of ice sheet history in the region. This pilot experiment demonstrates the feasibility of an innovative technique to delineate ice rise structure. Both direct and reflected P- and S-wave energy, as well as surface wave energy, are observed using a range of source offsets, i.e. a walkaway vertical seismic profile, recorded using fibre optic cable. Significant noise, which results from the cable hanging untethered in the borehole, is modelled and suppressed at the processing stage. At greater depth where the cable is suspended in drilling fluid, seismic interval velocities and attenuation are measured. Vertical P-wave velocities are high ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>V</mi><mi mathvariant="normal">INT</mi></msub><mo>=</mo><mn mathvariant="normal">3984</mn><mo>±</mo><mn mathvariant="normal">218</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="87pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="1c1cf091e7b3e5e25826df75b66763c9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-15-3443-2021-ie00001.svg" width="87pt" height="12pt" src="tc-15-3443-2021-ie00001.png"/></svg:svg> m s −1 ) and consistent with a strong vertical cluster fabric. Seismic attenuation is high ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" ...