A Seismic Refraction Profile Across the Polar Continental Shelf of the Queen Elizabeth Islands

Abstract

During the spring of 1967, a seismic refraction experiment was conducted from the SW tip of Prince Patrick Island in the Queen Elizabeth Islands of Arctic Canada to a point mid-way down the continental slope, some 220 km from the coast.It was found that seismic recording on sea ice was plagued by unusually high background noise levels which could be attributed to low frequency (below 1 Hz) oscillations of the ice pans and to the broad-band noise generated by frequent ice cracking. It was discovered, and is shown theoretically, that seismic wave propagating through a water layer (the ocean) and incident on the ice layer from below provide an exact π/2 phase shift between the horizontal and vertical components of surface motion. This fact can be used to advantage in digital processing.The interpretation shows a crustal model with depths to the M discontinuity of 28 ± 4 km at the coast, thinning to 15 ± 9 km at the end of the profile. The velocity of the mantle is measured as 8.05 ± 0.17 km/s. Mid-way down the continental slope there are 5.0 ± 1.63 km of sediments overlying material with a velocity of 5.36 ± 0.15 km/s. Material of a similar velocity, 5.72 ± 0.18 km/s, lies 2.7 ± 1.9 km beneath the surface material at the coast, where the surface layer has a velocity of 4.76 ± 0.4 km/s. It is concluded that the data support the hypothesis that the Canada Basin has an oceanic rather than a continental crust.