what is randy jolted from his sleep by

From the text:

What had jolted Randy from sleep-he would not learn all the facts for a long, a very long time after-were two nuclear explosions, both in the megaton range, the warheads of missiles lobbed in by submarines. The first obliterated the SAC base at Homestead, and incidentally sank and returned to the sea a considerable area of Florida’s tip. Ground Zero of the second missile was Miami’s International Airport, not far from the heart of the city. Randy’s couch had been shaken by shock waves transmitted through the earth, which travel faster than through the air, so he had been awake when the blast and sound arrived a little later. Gazing at the glow to the south, Randy was witnessing, from a distance of almost two hundred miles, the incineration of a million people. ch 5