Characterising ice slab in firn using seismic full waveform inversion, a sensitivity study

Pearce, Emma; Booth, Adam; Rost, Sebastien; Sava, Paul; Konuk, Tuğrul; Brisbourne, Alex ORCID: https://orcid.org/0000-0002-9887-7120; Hubbard, Bryn; Jones, Ian. 2023 Characterising ice slab in firn using seismic full waveform inversion, a sensitivity study. Journal of Glaciology, 85 (2). 15, pp. https://doi.org/10.1017/jog.2023.30

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Text (Open Access) © The Author(s), 2023. Published by Cambridge University Press on behalf of The International Glaciological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. characterising-ice-slabs-in-firn-using-seismic-full-waveform-inversion-a-sensitivity-study.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (5MB) | Preview

Abstract/Summary

The density structure of firn has implications for hydrological and climate modelling, and ice-shelf stability. The structure of firn can be evaluated from depth models of seismic velocity, widely obtained with Herglotz–Wiechert inversion (HWI), an approach that considers the slowness of refracted seismic arrivals. However, HWI is strictly appropriate only for steady-state firn profiles and the inversion accuracy can be compromised where firn contains ice layers. In these cases, full waveform inversion (FWI) may yield more success than HWI. FWI extends HWI capabilities by considering the full seismic waveform and incorporates reflected arrivals. Using synthetic firn density profiles, assuming both steady- and non-steady-state accumulation, we show that FWI outperforms HWI for detecting ice slab boundaries (5–80 m thick, 5–80 m deep) and velocity anomalies within firn. FWI can detect slabs thicker than one wavelength (here, 20 m, assuming a maximum frequency of 60 Hz) but requires the starting velocity model to be accurate to ±2.5%. We recommend for field practice that the shallowest layers of velocity models are constrained with ground-truth data. Nonetheless, FWI shows advantages over established methods, and should be considered when the characterisation of firn ice slabs is the goal of the seismic survey.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1017/jog.2023.30
ISSN:	0022-1430
Additional Keywords:	Glacier geophysics, Seismics, Seismology, Polar firn, Ice thickness measurement
Date made live:	12 Jun 2023 08:16 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533135

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