Number 6 (Story #4), October 25, 1990 by Phillip F. Schewe and Ben Stein PREDICTING EARTHQUAKES IS STILL A SHAKY SCIENCE. Prior to last year's Loma Prieta earthquake, scientists at the U.S. Geological Survey had predicted a 30% chance for a magnitude-6 earthquake in the Santa Cruz area sometime in the next 30 years. The quake that came was quite different: primarily vertical in nature (some areas west of the San Andreas fault rising by as much as two feet) rather than horizontal, 9 miles from the predicted center, and more powerful than expected (magnitude 7.1). Some scientists believe that the vigor of the quake effects as far away as San Francisco may have been due to reflections of the seismic waves from the crust-mantle boundary, much as light waves may undergo total internal reflection at a glass-water interface. The reflected waves then reinforced the seismic waves coming directly from the quake center. (The New York Times, October 23, 1990.)