A technique is described which involves traversing with fixed distances between the impact point and the 2 geophones. Both geophones are located on the same side of the impact point and at distance, greater than the critical distance for the refractor. In test surveys over magnesite deposits, a station interval of 50 ft was used, giving fixed distances of 50 and 100 ft from the impact point. This technique provides a useful and rapid reconnaissance tool for the investigation of shallow refractors under simple conditions.

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