Measurement of the downhole velocity of the CIROS-1 drillhole after the completion of drilling by lowering a hydrophone down the drillhole was unsuccessful due to equipment failure. Determination of the dip, faults and strong reflectors in the geologic structure in the immediate vicinity of the CIROS-1 drillhole was conducted using seismic reflection techniques. Testing of various seismic ... reflection techniques was also conducted for any future reflection projects on the sea-ice. It is important to link the geological structure determined by drilling with the horizons detected in other seismic surveys in the western Ross Sea, in order to date these horizons and their deformation. The reflection survey would also possible reveal some of the deformation history in the vicinity of the drillhole as well as the possible presence of reflecting strata at depths greater than reached by the drilling project. Two seismic lines were shot running at right angles from the CIROS-1 drillhole and records appear to have primary reflected energy down at least to 800m sub-seafloor. The aim was to determine the geological structure in the CIROS-1 immediate vicinity and to evaluate marine airgun sound sources as an alternative to explosive operation.