POINT PLEASANT BEACH, N.J. - Hurricanes or ferocious nor'easters pose the greatest threats of weather havoc in this region, but a moderate earthquake late last month has regional experts talking about a new someday threat.
The magnitude-3.9 temblor - with an epicenter 150 miles off Point Pleasant - rumbled and rolled Nov. 30 as it shook windows and rattled doorways from Beach Haven to Keyport.
While New Jersey has no violent fault lines like the San Andreas in California, its history points to a magnitude-5 or 6 quake hitting the region every 100 years or so, said Richard Dalton, a geologist with the New Jersey Geological Survey.
Records for the New York City area have been kept for 300 years, providing good information to modern geologists for estimating the frequency and intensity of earthquakes in New Jersey, Dalton said.
The most powerful earthquake to strike the region was the 5.5 temblor in 1884 known as the New York City earthquake, with an epicenter off Sandy Hook. That quake pulled buildings from their foundations, cracked masonry, and felled chimneys from Manhattan to West Chester, Pa.
Comparable was a 1737 quake that caused similar damage to the relatively few buildings in the region, Dalton said.
"Statistically we're overdue for a magnitude-4-plus earthquake, but whether it happens now or a year from now or a hundred years from now is impossible to predict," he said. "And just how much damage there would be is really anybody's guess. You have to rely on old newspaper articles from back then to try to figure out what really happened and then attempt to compare it with what happens today with relation to development, populations, and building codes."
Unlike California, which is on the front lines of a very active earthquake zone, New Jersey is at the geologic back end of that activity. But there is activity; some years as many as a dozen "cluster" earthquakes, albeit tiny ones, occur in the Garden State.
But the big one could happen here someday, said Alexander Gates, professor of earth and environmental sciences at Rutgers University-Newark.
"If you look at long periods of a geological history, you realize what you couldn't find or didn't think would occur does occur," Gates said. "And that tells us that anything is possible."
A Federal Emergency Management Agency assessment of risk exposure indicates that a magnitude-7 earthquake - similar to the 1995 quake in Kobe, Japan - could cause as much as $53 billion in damage in Monmouth County. Human casualties could be in the tens of thousands. Damage estimates for other New Jersey coastal communities were not available.
Gates and Dalton agreed that huge earthquakes were not something Garden State residents should be overly concerned about.
"There is risk, but certainly if you live in California, your exposure of the possibility of living where a major earthquake could hit is certainly greater than in New Jersey," Gates said.