Will the ground around New Jersey's Whitehouse Station continue to shake for the next few days? Almost certainly.
In fact, several small aftershocks have already occurred. But those aftershocks were around magnitude 2.0 and barely perceptible even to people standing very close to the epicenter.
Even larger aftershocks may occur.
The U.S. Geological Survey predicts a 45% chance of aftershocks of magnitude 3 or greater within the next week. Next year's probability increases to 66%.
Is this a sign of a devastating earthquake? Possibly, but unlikely.
Large earthquakes of magnitude 7 or greater are often preceded by small foreshocks. But so far, seismologists have not identified any distinguishing features of a particular earthquake that would warn of an impending larger quake.
If a devastating earthquake occurs next week, seismologists will retroactively call Friday's shaking a foreshock. However, there is no way to confidently predict major earthquakes in advance.
Seismologists also know that large earthquakes are rare in this part of the world. A 2008 study by scientists at Columbia University's Lamont-Doherty Earth Observatory found that in the New York City area, a magnitude 5 earthquake occurs about once every 100 years, a magnitude 6 or higher earthquake occurs about once every 670 years, and a magnitude 7 earthquake occurs about once every 670 years. It was revealed that an earthquake had occurred. Once every 3,400 years.
That is reflected in the Geological Survey's aftershock forecast, which currently says there is less than a 1 percent chance of a magnitude 6 or higher quake following Friday's quake. Even the odds of an equivalent magnitude 5 earthquake occurring are only 3 percent over the next week and 8 percent over the next year.
The predictions are updated as the instruments measure new seismic data.