Abstract: An exciting method for a logging by means of S wave is provided which includes inserting a wave source into a bore hole containing water and actuating an operating mechanism in the wave source to impart an exciting force to the bore hole wall in the direction perpendicular to the axis of the bore hole, so as to generate the S wave having characteristics of predominant radiation in the direction perpendicular to the axis of the exciting force. The improvement of the invention comprises abruptly ejecting the water at one side of the wave source intersecting the extension of the axis of the exciting force, while, simultaneously at the opposite side of the wave source, abruptly sucking the water of equivalent volume to that ejected at the first mentioned side, whereby a positive and negative pressure change are indirectly applied through the medium of the water to the two respective sides of the bore hole wall intersecting the extension of the exciting force axis.