has many known faults, but numerous smaller or deeply buried faults probably remain undetected. The stress that causes the earthquakes is generally considered to be derived from present-day rifting at the Mid-Atlantic ridge. In this model, pre-existing faults that were formed during ancient geological episodes, persist in the intraplate crust, and the earthquakes occur when the present-day stress is released along these zones of weakness. is generally considered to be due to ancient zones of weakness that are being reactivated in the present-day stress field. The NYC area is far from the boundaries of the North American plate, which are in the center of the Atlantic Ocean, in the Caribbean Sea, and along the west coast of North America. In contrast, east of the Rocky Mountains this is rarely the case. Earthquakes stronger than about magnitude 5.0 generate ground motions that are strong enough to be damaging in the epicentral area.Īt well-studied plate boundaries like the San Andreas fault system in California, scientists can often make observations that allow them to identify the specific fault on which an earthquake took place. earthquake, although uncommon, can be felt as far as 500 km (300 mi) from its epicenter, and can cause damage as far away as 40 km (25 mi) from its epicenter. earthquake typically can be felt as far as 100 km (60 mi) from its epicenter, but it infrequently causes damage near its source. contribute to the seismic energy propagating as much as ten times further than in the warmer rocks of California. The cooler rocks in the northeastern U.S. could be larger than the area of damage caused by an earthquake of the same magnitude in the western U.S. This means the area of damage from an earthquake in the northeastern U.S. are typically felt over a much broader region than earthquakes of the same magnitude in the western U.S. are 100 times lower than in California, but the earthquakes that do occur in the northeastern U.S.
The last major episode of geological activity to affect the bedrock in the NYC area occurred about 100 million years ago, during the Mesozoic era, when continental rifting that led to the opening of the present-day Atlantic Ocean formed the Hartford and Newark Mesozoic rift basins.Įarthquake rates in the northeastern U.S. Beginning about 200 million years ago, the present-day Atlantic Ocean began to form as plate tectonic forces began to rift apart the continent of Pangaea.
Between about 450 million years ago and about 250 million years ago, the Northern Appalachian region was affected by a continental collision, in which the ancient African continent collided with the ancient North American continent to form the supercontinent Pangaea. This complex structure was formed during the past half billion years when the Earth's crust underlying the Northern Appalachians was the site of two major geological episodes, each of which has left its imprint on the NYC area bedrock. The New York City area is part of the geologically complex structure of the Northern Appalachian Mountains. Green lines indicate the trace of the Ramapo fault.
Geological Survey (USGS) and the National Earthquake Information Center (NEIC). Seismicity in the vicinity of New york City. Thus, others have argued that the Ramapo Fault has not been demonstrated to be any more active than any other fault zones in the greater New York City area. Some seismologists have argued that this fault has the potential to produce a major earthquake, but earthquakes are scattered throughout this region, with no particular concentration of activity along the Ramapo fault (see Earthquake activity in the New York City area). 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. 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. The Ramapo Fault zone, spanning more than 185 miles (300 kilometers) in New York, New Jersey, and Pennsylvania, is a system of faults between the northern Appalachian Mountains and Piedmont areas to the east. Map depicting the extent of the Ramapo Fault System in New York, New Jersey, and Pennsylvania
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