A 1979 seismic event was a different kind of earthquake, and it is has intrigued scientists ever since. A new look at old data has provided some additional answers. On Feb. 24th, 1979, seismographs recorded a magnitude 3.8 earthquake under Randolph, Utah, located near the Idaho and Wyoming borders. Yet no one felt a thing and the seismic data made no obvious sense. Because its focal depth was 50 miles below sea level, the hypocenter wasn't in Earth’s crust, it was well into the upper mantle. rea