GERTZ: U.S. doubts Korean test was nuclear; Readings fall short of atomic explosion... MORE... U.S. intelligence agencies say, based on preliminary indications, that North Korea did not produce its first nuclear blast yesterday, WASHINGTON TIMES star reporter Bill Gertz is set to report in Tuesday editions. U.S. officials, speaking on the condition of anonymity, said that seismic readings show that the conventional high explosives used to create a chain reaction in a plutonium-based device went off, but that the blast's readings were shy of a typical nuclear detonation. 'There was a seismic event that registered about 4 on the Richter...