Near-surface seismic reflection profiling of the Matanuska Glacier, Alaska

Several common-midpoint seismic reflection profiles collected on the Matanuska Glacier, Alaska, clearly demonstrate the feasibility of collecting high-quality, high-resolution near-surface reflection data on a temperate glacier. The results indicate that high-resolution seismic reflection can be used to accurately determine the thickness and horizontal distribution of debris-rich ice at the base of the glacier. The basal ice thickness about 30% over a 300-m distance as the glacier flows out of an overdeepening. The reflection events ranged from 80- to 140-m depth along the longitudinal axis of the glacier. The dominant reflection is from the contact between clean, englacial ice and the underlying debris-rich basal ice, but a strong characteristic reflection is also observed from the base of the debris-rich ice (bottom of the glacier). The P-wave propagation velocity at the surface and throughout the englacial ice is 3600 m/s, and the frequency content of the reflections is in excess of 800 Hz. Supporting drilling data indicate that depth estimates are correct to within + or -1 m.