A method for generating seismic energy for subsurface surveying, comprising: operating a first seismic vibrator in a body of water; and operating at least a second seismic vibrator in a body of water substantially contemporaneously with the operating the first seismic vibrator, the operating the first and the at least a second seismic vibrators including applying a driver signal to each of the first and the at least a second seismic vibrators that are substantially uncorrelated with each other, each of the first and at least a second vibrators imparting energy into subsurface formations for detection after reflection from subsurface features, each of the first and the at least a second seismic vibrator having at least two resonance frequencies in a selected frequency band, each of the first and at least a second vibrators comprises: a flextensional outer shell, a magnetostrictive driver disposed within the outer shell, a first spring disposed within the outer shell and in functional contact with the driver, characterized in that each of the first and at least second vibrators further comprises a second spring disposed within the outer shell between the first spring and the outer shell, the second spring in functional contact with the driver and the outer shell, and wherein a mass load of the outer shell, a spring constant of the first spring and the second spring, and a mass load on the driver from the first spring are selected to result in the at least two resonance frequencies when the first and at least a second vibrators are disposed in a body of water. operating a first seismic vibrator in a body of water; and operating at least a second seismic vibrator in a body of water substantially contemporaneously with the operating the first seismic vibrator, the operating the first and the at least a second seismic vibrators including applying a driver signal to each of the first and the at least a second seismic vibrators that are substantially uncorrelated with each other, each of the first and at least a second vibrators imparting energy into subsurface formations for detection after reflection from subsurface features, each of the first and the at least a second seismic vibrator having at least two resonance frequencies in a selected frequency band, each of the first and at least a second vibrators comprises: a flextensional outer shell, a magnetostrictive driver disposed within the outer shell, a first spring disposed within the outer shell and in functional contact with the driver, characterized in that each of the first and at least second vibrators further comprises a second spring disposed within the outer shell between the first spring and the outer shell, the second spring in functional contact with the driver and the outer shell, and wherein a mass load of the outer shell, a spring constant of the first spring and the second spring, and a mass load on the driver from the first spring are selected to result in the at least two resonance frequencies when the first and at least a second vibrators are disposed in a body of water. a flextensional outer shell, a magnetostrictive driver disposed within the outer shell, a first spring disposed within the outer shell and in functional contact with the driver, characterized in that each of the first and at least second vibrators further comprises a second spring disposed within the outer shell between the first spring and the outer shell, the second spring in functional contact with the driver and the outer shell, and wherein a mass load of the outer shell, a spring constant of the first spring and the second spring, and a mass load on the driver from the first spring are selected to result in the at least two resonance frequencies when the first and at least a second vibrators are disposed in a body of water.