Abstract: Methods of detecting the presence and extent of hydrocarbon accumulations in subterranean formations are provided comprising introducing a first gas into the formation having the property of being substantially unreactive with the formation and with water contained therein but forming a combustible mixture with hydrocarbons and introducing a second gas into the formation having the property of being substantially unreactive with the formation and water but being explosively reactive with the first gas when mixed therewith in the presence of hydrocarbons. The second gas is mixed with the first gas in the formation and when in the presence of hydrocarbons the mixture explodes thereby generating seismic waves which travel through the earth to the surface thereof. The seismic waves are detected on the surface to thereby determine the presence and extent of the hydrocarbon accumulations in the subterranean formation.