In the spring of 2001, the CREWES project in conjunction with Devon Canada Ltd. (formerly Anderson Exploration Ltd.) and acquired a six kilometre test line (MKD-8), centred over the transition zone from floating to ground-fast ice in the Mackenzie Delta. Several different types of receivers, including 3-C geophones were laid out, and the entire line was shot with two tracked Vibroseis vehicles, and again with dynamite. A series of sweep tests and noise strips were also recorded. A hammer seismic survey of thirty meters length was also carried out, recorded by the 3-C geophones only. The hammer seismic survey included vertical hits on the ice, forty-five degree hits in opposite directions into forty-five degree V-shaped notches chopped into the ice, and tests hitting steel plates, wood blocks or the ice directly. Ice velocities from the hammer seismic profiles give P-wave values of 3137 m/s and S-wave velocities of 1900 m/s.
A preliminary analysis of dynamite and vibrator gathers has been made. The transition from ground-fast to floating ice has a profound (and deleterious) effect on seismic data quality. The vertical component of data recorded by the 3-C geophones for the vibrator source has been processed to a brute stack, and shows good reflectivity under the ground-fast ice. Reflections are also present under the floating ice, but have a poorer signal-noise ratio and less coherence. Frequencies up to at least 90 Hz are observed in the data. There is a distinct change in reflection character across the transition zone.
View full article as PDF (6.07 Mb)