Foreshock or Main Shock?

During a felt earthquake the adrenaline flows and the heart may palpitate. When the shaking stops, one wonders if that was it or if a worse earthquake is on the way. Many Fairbanksans during February 1977 must have had such thoughts. Many small earthquakes occurred in the area. At 11:14 a.m. on Sunday, February 27, there was a magnitude 4.2 shock and more than 30 lesser recorded earthquakes occurred during the next half hour.

Unfortunately there is, as yet, no way to tell if a particular earthquake is or is not a warning of a larger earthquake to follow. There have been instances of damaging earthquakes that have been followed within hours or days by great and destructive earthquakes. Once a large earthquake has occurred, it usually is followed by many lesser ones. These aftershocks are thought to result from rebounding of rocks that have been caused to move past an equilibrium position during the main shock.

For Fairbanksans there is some consulation in the knowledge that since the city was founded in 1902 there has never been severe earthquake damage. Nor has any one here yet been killed or perhaps even injured by an earthquake. We can hope that this record will stand for a long time.