Ice shelf structure derived from dispersion curve analysis of ambient seismic noise, Ross Ice Shelf, Antarctica

TitleIce shelf structure derived from dispersion curve analysis of ambient seismic noise, Ross Ice Shelf, Antarctica
Publication TypeJournal Article
Year of Publication2016
AuthorsDiez A., Bromirski PD, Gerstoft P, Stephen R.A, Anthony R.E, Aster R.C, Cai C., Nyblade A., Wiens D.A
JournalGeophysical Journal International
Date Published2016/05
Type of ArticleArticle
ISBN Number0956-540X
Accession NumberWOS:000375092400008
Keywordsactive reservoir beneath; anisotropy; antarctica; east antarctica; firn; glaciology; retreat; rift propagation; seismic anisotropy; stability; stream; subglacial lake whillans; surface; Surface waves and free oscillations

An L-configured, three-component short period seismic array was deployed on the Ross Ice Shelf, Antarctica during November 2014. Polarization analysis of ambient noise data from these stations shows linearly polarized waves for frequency bands between 0.2 and 2 Hz. A spectral peak at about 1.6 Hz is interpreted as the resonance frequency of the water column and is used to estimate the water layer thickness below the ice shelf. The frequency band from 4 to 18 Hz is dominated by Rayleigh and Love waves propagating from the north that, based on daily temporal variations, we conclude were generated by field camp activity. Frequency-slowness plots were calculated using beamforming. Resulting Love and Rayleigh wave dispersion curves were inverted for the shear wave velocity profile within the firn and ice to similar to 150 m depth. The derived density profile allows estimation of the pore close-off depth and the firn-air content thickness. Separate inversions of Rayleigh and Love wave dispersion curves give different shear wave velocity profiles within the firn. We attribute this difference to an effective anisotropy due to fine layering. The layered structure of firn, ice, water and the seafloor results in a characteristic dispersion curve below 7 Hz. Forward modelling the observed Rayleigh wave dispersion curves using representative firn, ice, water and sediment structures indicates that Rayleigh waves are observed when wavelengths are long enough to span the distance from the ice shelf surface to the seafloor. The forward modelling shows that analysis of seismic data from an ice shelf provides the possibility of resolving ice shelf thickness, water column thickness and the physical properties of the ice shelf and underlying seafloor using passive-source seismic data.

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