A method to enhance the horizontal spatial sampling, in a first horizontal direction, of the vertical motion component of seismic data on the free surface of the earth, comprising:
- a. measuring the vertical motion on the free surface of the earth and measuring the rotational motion on the free surface of the earth around a second horizontal axis orthogonal to the first horizontal direction;
- b. computing the gradient of vertical motion in the first horizontal direction by utilizing the measured rotational motion around said second horizontal axis and the relationships of spatial derivatives of displacement components at the free surface of the earth;
- c. reconstructing the horizontal sampling of the seismic wave field, by means of the Slope and Ordinate sampling technique, whereby the effective sampling is at a spatial sample spacing of half the physical spacing of the sensors in the first horizontal direction.