Characterizing Rayleigh Wave Velocity and Amplitude Anisotropy in an Alpine Glacier

Wednesday, 17 December 2014: 5:00 PM
Christina Ann Eilar1, Dylan Mikesell1, Alison E Malcolm2 and John Holloway Bradford3, (1)Massachusetts Institute of Technology, Cambridge, MA, United States, (2)Memorial University of Newfoundland, Earth Sciences, St John's, NL, Canada, (3)Boise State Univ, Boise, ID, United States
Regular patterns of fractures in solid materials induce seismic velocity anisotropy. These fracture patterns can also create azimuthally dependent attenuation in seismic amplitudes due to a preferential scattering direction. A parallel set of surface (or bed) crevasses in a glacier is an example of one such fracture pattern. These patterns are caused by the local strains within the glacier. In this study we analyze an active source 3D seismic survey recorded at Bench Glacier, Alaska, USA. We compare the Rayleigh group wave velocity as a function of azimuth and estimate that the mean velocity is 1672 m/s and 1% velocity anisotropy exists. We present an interpretation for the observed anisotropy by comparing our results with satellite imagery of the glacier in the survey area. Finally, we present the results of ongoing analysis of the Rayleigh wave amplitudes and compare with existing studies of glacier attenuation that do not take into account scattering attenuation when estimating the ice temperature from attenuation.