March quake in New Jersey was warning of 4.8 temblor
Small aftershocks likely to occur intermittently for next few weeks
That 2.2 earthquake New Jersey felt in March is now considered a foreshock to the larger magnitude 4.8 that rocked the state last week — and has since spawned some 50 aftershocks with more likely on the way, according to the U.S. Geological Survey.
Labeled a “foreshock,” the earthquake measuring a magnitude of 2.2 that struck near Whitehouse Station in Hunterdon County on March 15 is said to have been a precursor for the larger event at the same location April 5, which measured a magnitude of 4.8, authorities said. Timothy Clements, spokesperson for the U.S. Geological Survey, said that they retrospectively label an earthquake as a foreshock if a larger earthquake occurs shortly after in same geographic area.
“Only about 25 percent of earthquakes are preceded by foreshocks, so the occurrence of the earthquake on March 14 indicated that a larger, subsequent earthquake was possible, but not probable,” Clements said.
Aftershocks are far more common than foreshocks, according to David Robinson, physical geographer at Rutgers University.
“If only there were more minor foreshocks, for if so, they might alert us to a more prominent quake ahead, he said.
“There is nothing uncommon regarding the many aftershocks from last Friday’s quake.”
The day after the M4.8 quake, 30 aftershocks were detected, Clements said. Fifty total aftershocks have been noted as of Friday afternoon.
“There is nothing uncommon regarding the many aftershocks from last Friday’s quake.” David Robinson
“The rate of aftershocks decays with time,” Clements said.
“We expect there to be somewhere from none to a few aftershocks per day for the next week.”
But Clements said small aftershocks are likely to occur intermittently for the next few weeks and months before petering out. The survey’s aftershock forecast indicates that the chance of a M3 aftershock over the next year is about one in three.
Jenna Calderón covers breaking news and cold cases in Monmouth and Ocean counties. Before coming to the Press, she covered The Queen City for Cincinnati Magazine in Ohio. Contact her at 330-590-3903; jcalderon@gannettnj.com