Abstract: A high-frequency, high-repetition gas detonator is provided which is adapted for shallow seismographic work. The detonator comprises a detonation chamber, a rigid bottom plate adapted to be coupled to the earth, and a top plate positioned over the bottom plate. A plurality of springs resiliently hold the plates together whereby the bottom plate covers a bottom vent port in the chamber when the plates engage. The bottom plate opens the chamber to the surrounding medium when the plates disengage. Fluid conduit means communicate with the interior of the chamber for supplying thereto a pressurized detonating fluid. Means are provided for detonating the fluid thereby causing the bottom plate to move downward and separate from the top plate. The compressive force of the bottom plate sends a downward seismic pulse into the underlying layers of the earth. The products of detonation from the detonation chamber are vented outside through the cavity formed between the top and bottom plates when the plates are separted.