North Jersey region among ‘most active’ earthquake zones
Matt Fagan, Staff writer, @fagan_nj
Northern New Jersey, which straddles a significant ancient crack in the Earth’s crust known as the Ramapo Fault, recorded 16 earthquakes last year, an unusually high number for the area.
It had been relatively quiet this year, until geologists recorded a 1.3 magnitude quake last weekend in Morris Plains, and then a 1.0 magnitude quake Saturday in Morristown.
Last weekend’s tremor was reported by Columbia University’s Lamont-Doherty Observatory to the Morris Plains Police Department, which issued an advisory to residents on Monday morning.
Lamont-Doherty spokesman Kevin Krajick said the quake was pinpointed to a shallow depth of 6 kilometers just north of Grannis Avenue, between Mountain and Sun Valley ways, about 500 feet southeast of Mountain way School.
Rutgers Newark geology professor talks about earthquakes in northern New Jersey. Matt Fagan/NorthJersey.com
“It was a very small earthquake at a very shallow depth,” Krajick said. “Most people would not feel an earthquake that small unless they were absolutely right under it, if that.”
“To date (there) were no reported injuries or damage related to the earthquake and no Morris Plains residents reported any activity to this agency,” according to Morris Plains police Chief Jason Kohn
On the other hand, Butler Police Lt. Mike Moeller said his department received “a bunch of calls about it, between 9:30 and 10:30 p.m.”
Saturday’s earthquake was so minor that Morristown police said they received no calls from residents
Earthquakes are generally less frequent and less intense in the Northeast compared to the U.S. Pacific Coast, according to the New Jersey Department of Environmental Protection. But due to geological differences between the regions, earthquakes of similar magnitude affect an area 10 times larger in the Northeast compared to the West Coast.
The 16 tremors recorded in 2016 were minor, generally 1 or 2 magnitude, often misinterpreted as explosions, said Alexander Gates, geology professor at Rutgers University Newark campus.
“A lot of people in Butler felt them over the course of the last year, but a lot of them didn’t know it was an earthquake,” Gates said.
Butler is the borough, but also the name of the fault that sits at the end of aseries of others belonging to the Ramapo Fault, Gates said.
The Ramapo fault, Gates said, is the longest in the Northeast and runs from Pennnsylvania through New Jersey, snaking northeast through Hunterdon, Somerset, Morris, Passaic, and Bergen counties before coming to an end in New York’s Westchester County, not far from the Indian Point Energy Center, a nuclear power plant.
The small area, Gates said, is considered the most seismically active region east of the Mississippi based on data gathered since 1974, when seismographs were installed.
“I’d be willing to bet that you’d have to go all the way to Canada and all the way to South Carolina before you’d get one that active,” Gates said of the area which runs from the New York state line in the Ringwood and Mahwah area down to Butler and central Passaic County, Gates said.
Of last year’s 16 earthquakes, 12 were directly associated with the faults around Butler, Gates said.
Butler Councilman Ray Verdonik said area residents are well aware of the frequency of earthquakes and agrees they are often difficult to discern.
During one earthquake, the councilman said he and his neighbors rushed from their homes.
“We thought it was from Picatinny Arsenal or a sonic boom.” he said.
Won-Young Kim, director of the Lamont-Doherty Cooperative Seismographic Network, which monitors earthquakes in the Northeast, said often very shallow, the low magnitude quakes’ waves cause much ground motion. He said even though the waves don’t travel very far, they can seem more intense than the magnitude suggests.
They may not topple chimneys, he said but can crack foundations and frighten residents.
To put earthquake magnitudes in perspective, experts said each year there are about 900,000 earthquakes of 2.5 magnitude or less recorded annually by seismograph. These mild tremors are usually not felt.
There are 30,000 that measure between 2.5 and 5.4, and these are often felt, but cause minor damage.
About 500 quakes worldwide are recorded between 5.5 and 6 magnitude per year and cause slight damage to buildings and structures.
The 100 that fall within 6.1 and 6.9 may cause lots of damage in populated areas.
The 20 or so which fall within the 7 and 7.9 magnitude per year are considered major and cause serious damage.
Those that measure at 8 or greater can totally destroy communities near the epicenter and average one every five to 10 years.
The earthquake recorded in Mexico last week measured 7.1 magnitude.
Gates said he has identified most of the region’s numerous faults, but has yet to name them all. Among the unnamed include the faults responsible for last year’s quakes in the region.
Earthquakes in this region are intraplate ones, Gates said, meaning they occur within the plates. Earthquakes of this type account for more than 90 percent of the total seismic energy released around the world.
Plates are the masses of the earth’s crust that slowly move, maybe as little as a few centimeters a year to as much 18 centimeters, around the globe. Faults such as the San Andreas are interplate and occur near where two plates meet.
The plate North America rides upon runs from the Mid Atlantic Ridge to the Pacific Coast. The theory is that as plates interact with one another, they create stress within the plate. Faults occur where the crust is weak, Gates said. Earthquakes relieve the built up pressure.
Boston College Geophysics Professor John Ebel said he and a Virginia Tech colleague, believe the seismically active areas in New York and South Carolina are where some 200 million years ago, the plates tried to break off but failed. This led to a weakening of the earth’s crust which makes them susceptible to quakes.
While not predictable, the data collected seem to suggest earthquakes occur somewhat periodically, 40 active years followed by 40 less active, Gates said.
“We are over due for a 3 or 4” magnitude, Gates said. “A 4 you’d feel. It would shake the area. Everybody would be upset.”
Ebel does not fully agree. He said saying “overdue” might be somewhat misleading. Earthquakes happen through a slow process of rising stress, “like dropping individual grains of sand on the table.”
You never know which grain will cause the table to break, he said.
Still all three experts say statistically it is only a matter time before a magnitude 5 quake is recorded in the northern New Jersey area.
The scientists said quakes in the Northeastern part of the United States tend to come 100 years apart and the last one was recorded in 1884 believed to be centered south of Brooklyn. It toppled chimneys and moved houses from their foundations across the city and as far as Rahway.
Washington D.C. experienced a 5.8 magnitude quake in 2011, which was felt in the Northeast, Gates said. That quake cracked the Washington Monument.
A similar quake was recorded in 1737 in Weehawken, Gates noted.
“Imagine putting a 5.5 magnitude earthquake in Weehawken, New Jersey next to the Bridge, next to the tunnel,” Gates said. “Boy that would be a dangerous one.”
In 2008 Columbia University’s The Earth Institute posted an article titled: “Earthquakes May Endanger New York More Than Thought, Says Study.”
“Today, with so many more buildings and people, a magnitude 5 centered below the city would be extremely attention-getting,” the article’s co-author John Armbruster wrote. “We’d see billions in damage, with some brick buildings falling.”
The threat though, is not tangible to many, Armbruster wrote.
“There is no one now alive to remember that last one, so people tend to forget. And having only a partial 300-year history, we may not have seen everything we could see. There could be surprises — things bigger than we have ever seen,” Armbruster wrote.
The Earth Institute’s article did note New York City added earthquake-resistant building codes in 1995.
New Jersey also began to require earthquake-resistant standards in the 1990s. The state, following the 2011 Virginia quake, now requires lake communities to make dams able to withstand a magnitude 5 earthquake.
The issue, Gates said, is that many of the buildings were built before these codes went into effect. A “sizable” earthquake could cause much damage.
Then there’s the prediction that every 3,400 years this area can expect a quake at 7 magnitude.
According to the Earth Institute article, a 2001 analysis for Bergen County estimates a magnitude 7 quake would destroy 14,000 buildings and damage 180,000 in that area alone. Likewise, in New York City the damage could easily hit hundreds of billions of dollars.
Ebel noted that depending on the depth and power of a severe quake, damage could be also be wide ranging. In 2011, Washington D.C., 90 miles away from the epicenter, which was located in central Virginia, suffered significant damage. Cities like Philadelphia fall within that radius.
“The big one could happen tomorrow or 100 years from now. That’s the problem,” Gates said. It geological terms 100 years is just a spit in the ocean, he noted.
Then again North Jersey is more likely to be hit by hurricane in the next three years, Gates added.
Staff Writer William Westhoven contributed to this report.
New Jersey’s top earthquakes
• Dec. 19, 1737 — Weehawken, believed to be a 5-plus magnitude quake, could be very serious if occurred in same spot today.
• Nov. 29, 1783 — Western New Jersey. Geologists are not exactly sure where it happened because area was sparsely populated. Estimated magnitude varies from 4.8 to 5.3. Felt from Pennsylvania to New England.
• Aug. 10, 1884 — A 5.2 earthquake occurred somewhere near Jamaica Bay near Brooklyn. The quake toppled chimneys and moved houses off their foundations as far Rahway.
• The biggest earthquake in the last 45 years of data available form USGS was a 3.8 quake centered in Carneys Point in Salem County on the morning of Feb.28, 1973
• New Jersey has never recorded a fatality due to an earthquake, according to the DEP.
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North Jersey region among ‘most active’ earthquake zones