A seismic instrument sensing unit mounting assembly includes an outer housing having an inner spherical chamber with an inner housing having a low center of gravity and a semi-spherical bottom surface cooperatively engaging the spherical walls of the outer housing for sliding thereon to the lowermost point within the spherical chamber and thereby maintain a vertical orientation. A sensing unit having a sensing axis with a preferred vertical orientation mounted within the inner housing such that the unit is maintained with the sensing axis in the vertical orientation regardless of the position or orientation of the outer housing. A number of these self-erecting sensing units are connected together by a suitable tension and conductor cables and are deployed and picked up by a method employing mechanical means. The string of units are rapidly layed out upon the surface of the earth without regard to the orientation of the outer housing.