This abstract describes vibrator systems for generating elastic waves in the earth, in which an actuator has a mechanical output drive means responsive to an electrical oscillatory signal, the drive means operates a variable volume compartiment filled with fluid, which is connected by conduit to a least one vibrator, comprising an expandable closed chamber connected between a base plate and a reaction mass. Two or more compartments can be used with two or more actuator drive means, the compartments connected separately to a plurality of vibrators. The vibrators may operate in-phase on in phase opposition. The plurality of vibrators may operate in horizontal and/or vertical arrays.