A seismic vibrator, comprising: a base plate; a mass movably disposed relative to the base plate for imparting vibrational energy thereto; and an actuator coupled to the mass for moving the mass relative to the base plate; characterised by: the base plate being elongated and having a longitudinal axis; the seismic vibrator further comprising: a first sensor disposed on the base plate and detecting first signals indicative of acceleration imparted to the base plate, the first sensor disposed at a location on the base plate experiencing transition between flexing along the longitudinal axis during vibration of the base plate; a second sensor disposed on the mass and detecting second signals indicative of acceleration of the mass; and a controller communicatively coupled to the actuator and the first sensor, the controller controlling the vibrator based at least in part on the first signals from the first sensor, wherein the controller is communicatively coupled to the second sensor and computes a weighted-sum ground force based on acceleration values from the first and second signals and based on mass values for the mass and the base plate; and by the base plate comprising a plurality of beams disposed parallel to one another along the longitudinal axis, each of the beams having a height that is at least equal to or greater than 10% of a longitudinal length along which the beam bends during vibration of the base plate a base plate; a mass movably disposed relative to the base plate for imparting vibrational energy thereto; and an actuator coupled to the mass for moving the mass relative to the base plate; characterised by: the base plate being elongated and having a longitudinal axis; the seismic vibrator further comprising: a first sensor disposed on the base plate and detecting first signals indicative of acceleration imparted to the base plate, the first sensor disposed at a location on the base plate experiencing transition between flexing along the longitudinal axis during vibration of the base plate; a second sensor disposed on the mass and detecting second signals indicative of acceleration of the mass; and a controller communicatively coupled to the actuator and the first sensor, the controller controlling the vibrator based at least in part on the first signals from the first sensor, wherein the controller is communicatively coupled to the second sensor and computes a weighted-sum ground force based on acceleration values from the first and second signals and based on mass values for the mass and the base plate; and by the base plate comprising a plurality of beams disposed parallel to one another along the longitudinal axis, each of the beams having a height that is at least equal to or greater than 10% of a longitudinal length along which the beam bends during vibration of the base plate the base plate being elongated and having a longitudinal axis; the seismic vibrator further comprising: a first sensor disposed on the base plate and detecting first signals indicative of acceleration imparted to the base plate, the first sensor disposed at a location on the base plate experiencing transition between flexing along the longitudinal axis during vibration of the base plate; a second sensor disposed on the mass and detecting second signals indicative of acceleration of the mass; and a controller communicatively coupled to the actuator and the first sensor, the controller controlling the vibrator based at least in part on the first signals from the first sensor, wherein the controller is communicatively coupled to the second sensor and computes a weighted-sum ground force based on acceleration values from the first and second signals and based on mass values for the mass and the base plate; and by a first sensor disposed on the base plate and detecting first signals indicative of acceleration imparted to the base plate, the first sensor disposed at a location on the base plate experiencing transition between flexing along the longitudinal axis during vibration of the base plate; a second sensor disposed on the mass and detecting second signals indicative of acceleration of the mass; and a controller communicatively coupled to the actuator and the first sensor, the controller controlling the vibrator based at least in part on the first signals from the first sensor, wherein the controller is communicatively coupled to the second sensor and computes a weighted-sum ground force based on acceleration values from the first and second signals and based on mass values for the mass and the base plate; and by the base plate comprising a plurality of beams disposed parallel to one another along the longitudinal axis, each of the beams having a height that is at least equal to or greater than 10% of a longitudinal length along which the beam bends during vibration of the base plate