Waiting for Parkfield to quake

After dark on November 16, a media van collided with a cow while driving through earthquake country near Parkfield, Calif. That may have been the most damaging incident to occur during the 72-hour earthquake alert issued, on November 14, by the state's Office of Emergency Services (OES). Officials issued the Level A alert—meaning there was a one in three chance of a magnitude-6 quake within 3 days—following a 4.8-magnitude quake in the town of Parkfield, on the San Andreas fault. The probability of a bigger quake dies off rapidly with time. And, although the anticipated tremor never came, seismologists wrote another chapter in earthquake analysis and prediction in this seismically perilous state.