Transcript for Computer Animation of Loma Prieta Aftershocks, segment 02 of 12


At five oh four P. M. on October seventeenth, nineteen eighty-nine, the magnitude seven point one Loma Prieta earthquake shook the San Francisco Bay area. It was the largest earthquake in central California since the nineteen oh six San Francisco earthquake. It killed sixty-seven people and caused several billion dollars in damage. This video shows what seismology can tell us about the Loma Prieta earthquake and its aftershocks and how they relate to typical seismicity in the rest of California.

In nineteen eighty-eight the U. S. Geological Survey published a report estimating the probabilities of future large earthquakes along the San Andreas Fault in the next thirty years. The fault was divided into segments where large earthquakes have occurred or are likely to occur. This probability map shows that the Parkfield segment was considered to be the most likely to slip in a magnitude six earthquake. The southern Santa Cruz Mountain segment was identified as the site of a magnitude six and a half to seven earthquake with a thirty percent probability within thirty years. This means that the Loma Prieta earthquake was anticipated. The probability of the Loma Prieta earthquake was the highest of any earthquake in the San Francisco Bay area.