Fast-paced action, which I could not seem to get enough in my teens.

"Earthquake country" said the Professor. "San Francisco is geologically and seismologically a city that waits to die. Los Angeles is ringed by earthquake centres -- seven massive 'quakes so far. We have no idea where the next, the monster, will hit…." Until a criminal fanatic kidnaps a nuclear scientist and builds his own atomic bombs. If exploded on California's fault lines they could trigger off the mightiest earthquake of them all -- killing half its population and dumping the entire city of San Francisco in the sea.