A three-axis seismic vibrator is provided which imparts compressional and shear wave seismic vibrations, either sequentially or simultaneously, into the Earth's surface. The seismic vibrator includes an earth-contacting baseplate which transmits vibrational energy into the Earth's surface; a support structure; a vibrator assembly pivotally supported at one end by the support structure; and servo-hydraulic control circuits which activate reciprocal vibration along the vibratory axis of the vibrator assembly and sustained oscillatory vibration of the vibrator assembly. The vibrations thus generated are transferred to the baseplate and injected into the Earth's surface. These vibrations and their reflections can then be recorded and analyzed to determine the mineral content of the Earth's surface in the immediate area.