The questions were coming fast and frantic: How strong was the earthquake? Was it on the San Andreas? Is the Big One coming? A massive temblor had struck near Joshua Tree shortly before 10 p.m., causing buildings to sway all the way to Las Vegas. As the public braced for more shaking, the media flocked to Caltech that night in 1992. One woman seemed to have all the answers. It was a magnitude 6.1, explained U.S. Geological Survey seismologist Lucy Jones, and the odds of a larger quake in the next three days stood at 15%. She shifted her weight...