Abstract: A detonation system especially useful for initiating a plurality of substantially simultaneous seismic detonations includes an electric trunkline circuit disposed on the surface of a firing site containing boreholes, within which booster charges having respective top and base portions are disposed. The booster charges are connected without intervening detonators to the downhole ends of equal-sized lengths of low-energy detonating cord, the surface ends of which are connected to semiconductor bridge-initiated electric detonators connected in series in the firing circuit. The resulting system, because of the small deviation in function time of the semiconductor bridge detonators, has greatly reduced scatter time as compared to prior art systems utilizing conventional downhole electric detonators, and has a safety advantage in that the boreholes are free of detonators.