Krista Pasfield
State University of New York at Stony Brook
Nicoll’s Rd., Stony Brook,NY
Introduction
Contrary to popular belief, Long Island and New York have a fair share of earthquakes, and this research set out to prove it. Not only was the data conclusive to this, but it revealedmore seismic activity
than previously hypothesized.
An earthquake is a sudden, often violent movement of the earth’s surface as a result of the release of energy from the earth’scrust. The cause of this is that the earthis always bendingslightly from tectonicforces.
When this stressor pressure exceeds the strength of the rocks, the crust breaks and can snap into a new position. Vibrations from this are called seismic waves, which travel through and along the earth’s surface. These seismicwaves are called earthquakes (Bolt1993).
Earthquakes often occur at faults. A fault is where two large blocks of crustal rock have slippedor moved against each other. They can move up and down or horizontally to the left and right. Essentially, faults are weaknesses in the crust. The three main kinds of faultsare strike-slip, dip-slip,and thrust fault.
More than 1,000,000 earthquakes occur worldwide in one year (Berlin 1980). This number includesquakes too small to be felt but large enough to be recorded as an earthquake. Ninety-five percent ofthem are along tectonic or crustal plate boundaries. Major boundaries include California, Alaska, Japan, west coast South America and the Philippines. Four thousand of these earthquakes occur in Alaska alone. Alaska happens to be located over a subduction zone, which is where one plate is sliding over another. The largest earthquake the U.S. has ever experienced was in Alaska. Earthquakes are quite common natural events, contrary to what some people might believe. They can occur as deep as 5,000 miles below the surface.
Seismologists are scientists who study earthquakes. They use two different names to describe the types of waves that are given off by the earthly vibrations. The first is a P-wave, primarypreliminary waves, which is the first to arriveat a seismic stationafter movement. It compresses and dilates the rock as it travels.Its usual speed is less than 6km/s in the crust and can get up to 13km/s traveling through the core. The speed is comparable to that of sound waves. S-waves, second preliminary waves, follow a similar path to that of the P-waves,though it is believed that they can’t travel through the core. These waves shake the rock sideways as it advances at half the speed of a P-wave. A combination of these two waves is used to locate the epicenter of an earthquake, based on their time intervals. The epicenter is most easily described as the spot of a rock hitting the water when tossed into a still pond. The surrounding waves represent the P and S waves (Bolt 1988). The waves are measured using a seismometer, which senses the earth’s motion, and a seismograph, which combines with the seismometer to obtain a printout.
Seismology of New York and Long Island
There are earthquakes in New York and on Long Island. The Ramapo fault runs from Westchester County to the Hudson River at Stony Point. It is a hairline fracture, 50 miles long, compared to the San Andreas faultof California, which is 700 miles long. The Ramapois one of the oldestfaults, being 1 billion years old. It was very active200 million yearsago, and startingin the 1970’s, began to act up again. This fault is located a mere 35 miles from New York City, but people don’t seem to worry about it (Heppenheimer 1988). (Figure 1)
It is also now believed that the belt of rocks surrounding New York City have brokeninto two major faults, the St. Nicholas Thrust and Cameron’s Line. Future seismic activity may occur among these Northwest trending(running) faults. The rock that these faults are located in is eroded Proterozoic to Lower Paleozoic,andthis type of rock widens as you move northeastward. The means of separating these two forms of rock is the ductileSt. Nicholas thrust and Cameron’s Line (Neibling 1999). They were developed during a long process of deformation and folding, which is an extremely slow form of faulting. Cameron’s Line shows this to the extreme in western Queens and Brooklyn. There is a "famous" 14th Street fault that commands the low structures between Manhattan’s 23rd and Canal streets. (Figure 2) New York City and its’ vicinity isnot safe from the hazards of seismic activity. The Ramapo fault is also responsible for New Yorkers to be able to live where they do because it’s height, however slight,prevented the sea from fillingin the Newark basin, which was formed around the same time (Sullivan 1985).(Figure 3)
Plate tectonics is the widely accepted theory that the crust of the earth is divided into rigid plates that are constantly in motion, moving continents and ocean basins. Where two of these plates meet, rubbingcan occur, which causes an earthquake. Scientists are not sure, then, how earthquakes occur in New York. North America is located in the middle of a plate that stretches from California to the mid-Atlantic, but platescould still be responsible for our earthquakes. The New Madridarea, which is the centralpart of the U.S., has had some of the worst quakes the countryhas ever experienced, and it is located in the middleof the plate as well (Levy 1995).(Table 1)
East Coast quakes have never produced surface-visible disruptions, unlike the San Andreas Fault of California. Because the crust on the East coast is cooler and more rigid, earthquakes are generally felt over a larger area than those on the West coast, since these conditions allow seismic waves to travel further, but they do so with less force.Seismic wave velocities are also related to the type of rock, the temperature, and the pressureconditions under which they occur (Weidner 1999).
Studies of earthquakes on various instruments are increasing as the numbers of quakes are. A concerninvolves Consolidated Edison’s nuclear power plant at Indian Point. Should an earthquake cause adisruption in the cooling system, radioactive gases would be released into the atmosphere. In addition,buildings like the World Trade Center were not built in accordance with recommended earthquakeguidelines.Whileitcanwithstandupto150-mphwinds,thatwoulddonothingtoprotectitintheeventofa substantial earthquake. (Figure 4a) It was just in recent years that people have started to recognize thepossibilityofanearthquakeinNewYork.(Figure4b
The materials of the rock do not affect the probability of having an earthquake, though it does affect how the earthquake will be felt, and how severethe sink and rise damageis. Long Islandsits on a bed of sand and water, which amplifies waves and makes it susceptible to liquidfaction in the case of a major event."Eastern quakes shake over bigger distances because the upper mantle and lower crust here (30-100 km deep) are cooler.This is because the east is less geologically active;older", says Dr. Dan Davisof SUNY Stony Brook. The first correct prediction in the United States was of a 2.6 magnitude at Blue Mountain Lake, NY.
Historical Perspective
1779 had the oldest earthquake published about in modern Newsday. On February 2nd,a 3.5 rumble shook northern New Jersey and Long Island. It was centered in Cheesequake State Park, NJ. No injuries or damage was reported. (Brasley 1979) Often times, people in NYC just assume that tremors are the resultof normal traffic vibrations, and people of the island chalk it up to a passing truck. People don’t expect earthquakes in New York, but to prove this thinking incorrect, one of the best sources is first hand accounts. From Sketches from Local History, a man writes about Nathan Ropping Cook, a man who built a house somewhere between 1793 and 1800 on Long Island, and the earthquake that occurred during that time period. He also describes that, in the aftershock of one he experienced, graves were 15 to 20 inches out of line in the Seuttle Hole graveyard. Ponds supposedly settled towards the center of the chain they were locatedon.
Another one of a Sunday afternoon in August of 1882 had north to south waves and upset some vases and dishes. Distinct sulfur smells were also said to be quiteperceptible. New York City was also rockedby a
5.0 earthquakeon August 10,1884,which caused some considerable damage. February 28th, 1925 at 9:22 another north to south quake occurred, swinging lamps and pictures, as well as nauseating some people.
October 22, 1981 had to the most powerful quake to hit Long Island since 1937, and possibly the strongest in a hundred years. It measured a 3.5 on the Richterscale, and the epicenter was in the Long IslandSound. It occurred at 12:49 PM, and did no major damage, though some plaster cracked, and a chandelier fell (Gatewood 1981). (Figure 6) In New Brunswick, New Jersey, a quake struck and was felt in most of the eastern provinces of Canada and in New England as a result of its’ 5.9 degree shock waves.(Sommer 1982) Another earthquake occurred on October 8, 1983. It was felt from Quebec to Baltimore, though most residents of Long Island slept through the 6:18 AM tremor. The 5.2 quake was centered near Blue Mountain Lake, NY. This particular disturbance was caused by a coin-shaped mass of rock that slipped a few inches approximately 10 miles below the earth’s surface. Shock waves were measured for about 10 minutes at Stony Brook.(Freedman 1983)
On October 24, 1985, a 4.0 earthquake rattled Smithtown, New York (Long Island) at about 6:07am. It was the largest to hit the area in 48 years. Its epicenter was in Ardsley, New York, which was located in northernWestchester County. The shaking lasted for less than a minute. (Wojtas1985) On June 18, 1991, an earthquake centered 40 miles west of Albany shook three states, and measured between a 3.9 and 4.4 on the Richter scale. (NY Times)
The year 1992 was also had a number of earthquakes. On March 11, a quake centered 15 miles south of Montauk registered a 2.8 tremor. It occurredat 6:51 p.m. according to Prof. Don Weidner of SUNY Stony Brook. It was centered about 15 miles south of Montauk and measured a 2.8 on the Richter scale. The quake was felt in Connecticut, and picked up by seismometers in Massachusetts and New Hampshire. (Mintz 1992)
Data and Discussion
So, where were you on January 28, 1999? If you were on Long Island, you would have been standing over seismic waves rumbling through the rock to be registered on the seismograph located in the basement of the Earth and Space Sciences(ESS) building at SUNY Stony Brook. It occurred at 8:10 p.m. at 52.92Nand 177.73W. It was a magnitude 6.60 quake.
On March 8, 1999, another earthquake was recorded on the seismometer located at Stony Brook University. This one was centered in the Kodiak Island region of Alaska, at approximately 58.337N and 151.710W. Ten stations were used to determine its’ epicenter. The epicenter was located about 47 kilometers down inside the earth. It occurred at 13:03:47.5 GMT. March 20, 1999, had another earthquake recorded on the Stony Brook seismometer. This one occurred at 10:47:45 GMT, and was located at 51.61N and 177.73W, which is Andreanof Island, of the Aleutian Islands of Alaska. It registered a 6.8 on the Richter scale. The next earthquake, on March 31, 1999, was locatedjust south of Panama. It was at 5.80N and 82.30W. The quake registered a 6.0 on the Richter scale. A 2.9 earthquake occurredin South Carolinaon the 29th of March.
On March 8, 1999, another earthquake was recorded on the seismometer located at Stony Brook University. This one was centered in the Kodiak Island region of Alaska, at approximately 58.337N and 151.710W. Ten stations were used to determine its’ epicenter. The epicenter was located about 47 kilometers down inside the earth. It occurred at 13:03:47.5 GMT. March 20, 1999, had another earthquake recorded on the Stony Brook seismometer. This one occurred at 10:47:45 GMT, and was located at 51.61N and 177.73W, which is Andreanof Island, of the Aleutian Islands of Alaska. It registered a 6.8 on the Richter scale. The next earthquake, on March 31, 1999, was locatedjust south of Panama. It was at 5.80N and 82.30W. The quake registered a 6.0 on the Richter scale. A 2.9 earthquake occurredin South Carolinaon the 29th of March.
Long Island definitely had its share of earthquakes, and is a very open-armed receiver of the shock waves of others. (Figure 7) Almost every visit revealed yet another event. The data collected proved that Long Islandhas and receives more earthquakes than previously hypothesized. It is time that people start to take noticeof this and take steps to protectthemselves in the event of a seismicevent of significance.
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