The fault that ruptured beneath New Jersey on Friday morning was likely an ancient, sleeping seam in the Earth, awakened by geologic forces in a region where earthquakes are rare and seismic risks are not fully understood. 

The magnitude-4.8 earthquake was the strongest in New Jersey in over 200 years. 

The United States Geological Survey said in a news conference that more earthquakes are possible, with statistical modelers estimating a 3% chance of an earthquake of magnitude 5 or higher in…