Abstract: Seismic waves are generated by detonating an explosive gas mixture in an earth cavity formed by driving a short earth auger to a desired depth, leaving most of the augered earth in the hole surrounding the auger shaft, and then pulling the auger and shaft upwardly to lift and compress the augered earth and pack it around the auger shaft, thereby forming and sealing the cavity below the auger. The gas mixture is then introduced through the hollow auger shaft and detonated, preferably by ignition propagation through the connecting hose and the auger shaft. Upon completion of as many gas fills and detonations as may be desired, the auger is reversed and withdrawn, leaving the ground surface virtually undisturbed.