Ice shelf structure from dispersion curve analysis of passive-source seismic data, Ross Ice Shelf, Antarctica

Monday, 14 December 2015
Poster Hall (Moscone South)
Anja Diez1, Peter D Bromirski2, Peter Gerstoft2, Ralph A Stephen3, Robert E Anthony4, Richard C Aster5, Chen Cai6, Andrew Nyblade7 and Doug Wiens6, (1)Scripps Institution of Oceanography, La Jolla, CA, United States, (2)University of California San Diego, La Jolla, CA, United States, (3)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (4)New Mexico Tech, Socorro, NM, United States, (5)Colorado State University, Geosciences Department, Fort Collins, CO, United States, (6)Washington University in St Louis, Department of Earth and Planetary Sciences, St. Louis, MO, United States, (7)Penn St Univ, University Park, PA, United States
An L-shaped array of three-component short period seismic stations was deployed at the Ross Ice Shelf, Antarctica approximately 100 km south of the ice edge, near 180° longitude, from November 18 through 28, 2014. Polarization analysis of data from these stations clearly shows propagating waves from below the ice shelf for frequencies below 2 Hz. Energy above 2 Hz is dominated by Rayleigh and Love waves propagating from the north. Frequency-slowness plots were calculated using beamforming. Resulting Love and Rayleigh wave dispersion curves were inverted for the shear wave velocity profile, from which we derive a density profile. The derived shear wave velocity profiles differ within the firn for the inversions using Rayleigh and Love wave dispersion curves. This difference is attributed to an effective anisotropy due to fine layering. The layered structure of firn, ice, water, and ocean floor results in a characteristic dispersion curve pattern below 7 Hz. We investigate the observed structures in more detail by forward modeling of Rayleigh wave dispersion curves for representative firn, ice, water, sediment structures. Rayleigh waves are observed when wavelengths are long enough to span the distance from the ice shelf surface to the seafloor. Our results show that the analysis of high frequency Rayleigh waves on an ice shelf has the ability to resolve ice shelf thickness, water column thickness, and the physical properties of the underlying ocean floor using passive-source seismic data.