Map depicting the extent of the Ramapo Fault System in New York, New Jersey, and Pennsylvania
The Ramapo Fault, which marks the western boundary of the Newark rift basin, has been argued to be a major seismically active feature of this region, but it is difficult to discern the extent to which the Ramapo fault (or any other specific mapped fault in the area) might be any more of a source of future earthquakes than any other parts of the region. The Ramapo Fault zone spans more than 185 miles (300 kilometers) in New York, New Jersey, and Pennsylvania. It is a system of faults between the northern Appalachian Mountains and Piedmont areas to the east. This fault is perhaps the best known fault zone in the Mid-Atlantic region, and some small earthquakes have been known to occur in its vicinity. Recently, public knowledge about the fault has increased – especially after the 1970s, when the fault’s proximity to the Indian Point nuclear plant in New York was noticed.
There is insufficient evidence to unequivocally demonstrate any strong correlation of earthquakes in the New York City area with specific faults or other geologic structures in this region. The damaging earthquake affecting New York City in 1884 was probably not associated with the Ramapo fault because the strongest shaking from that earthquake occurred on Long Island (quite far from the trace of the Ramapo fault). The relationship between faults and earthquakes in the New York City area is currently understood to be more complex than any simple association of a specific earthquake with a specific mapped fault.
A 2008 study argued that a magnitude 6 or 7 earthquake might originate from the Ramapo fault zone, which would almost definitely spawn hundreds or even thousands of fatalities and billions of dollars in damage. Studying around 400 earthquakes over the past 300 years, the study also argued that there was an additional fault zone extending from the Ramapo Fault zone into southwestern Connecticut. As can be seen in the above figure of seismicity, earthquakes are scattered throughout this region, with no particular concentration of activity along the Ramapo fault, or along the hypothesized fault zone extending into southwestern Connecticut.
Just off the northern terminus of the Ramapo fault is the Indian Point Nuclear Power Plant, built between 1956 and 1960 by Consolidated Edison Company. The plant began operating in 1963, and it has been the subject of a controversy over concerns that an earthquake from the Ramapo fault will affect the power plant. Whether or not the Ramapo fault actually does pose a threat to this nuclear power plant remains an open question.