A refraction type of seismic shooting used to facilitate the separation of intercept times into constituent delay times. Three profiles can be laid out as sides of a triangle. If intercept times are obtained at each of the vertices of the triangle from shots at the other two vertices, one can solve for the delay times at the three corners. Delay times along the 3374 sides of the triangle can be determined by taking differentials in the intercept times with respect to the delay times established at the vertices.