THE FRIDAY INTEL
Friday, March 14, 2026
Westchester sits on one of the most active fault systems in the northeastern United States. Here’s what the seismic data actually shows.
What’s Underneath Westchester — The Seismic Data Nobody Talks About
Tuesday’s magnitude 2.3 earthquake in Sleepy Hollow was small. No damage, no injuries, no story by Wednesday. But the data underneath that event tells a much bigger story about the ground Westchester County sits on.
The Fault Lines Are Real
Westchester sits on the Ramapo Fault system, a 185-mile seismic corridor running from Pennsylvania through New Jersey and into the county. It is the most seismically active fault system in the northeastern United States. Over the past 56 years, the USGS has recorded an average of 2.8 earthquakes per year in this immediate area. One hits magnitude 3.0 or higher roughly every eight years.
The Dobbs Ferry Fault, mapped along the eastern Hudson riverbank through Westchester, produced a magnitude 4.0 earthquake in Ardsley in 1985 that was felt in Philadelphia and southern Canada. And in 2008, Columbia University’s Lamont-Doherty Earth Observatory discovered a previously unknown seismic zone running 25 miles from Stamford, Connecticut to Peekskill, New York — passing less than one mile from Indian Point. Based on that research, Columbia seismologists estimated that a magnitude 5.0 earthquake occurs in this area once every 100 years and a magnitude 6.0 once every 670 years.
The Building Problem
New York did not adopt seismic building code provisions until 1995. California started in 1925. While modern construction now meets stringent standards, the majority of buildings in Westchester predate those codes. FEMA estimates that unreinforced masonry buildings — the brick and stone structures that define downtowns from Tarrytown to Yonkers — account for 75% of all building losses in a magnitude 7 earthquake. And because the Northeast’s dense, ancient bedrock conducts seismic energy far more efficiently than the West Coast’s younger geology, earthquakes here are felt 4 to 5 times farther from the epicenter than equivalent events in California.
What This Means for You
Tuesday’s quake was routine. The risk of a larger event is not. The last magnitude 5+ earthquake in the greater New York area was in 1884 — 142 years ago. Columbia’s data puts the average recurrence at once per century. If you own older masonry property in Westchester, it is worth understanding your seismic exposure. FEMA publishes retrofit guidelines for unreinforced buildings, and standard homeowner insurance typically does not cover earthquake damage without a separate rider. Indian Point is closed but still being decommissioned, with spent fuel on site. The NRC kept it in its highest seismic evaluation category for a reason.
The ground under Westchester is more active than most residents realize. The data has been there all along.
Did you feel Tuesday’s quake? Reply and tell me where you were when it hit.
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Sources: USGS, Columbia University Lamont-Doherty Earth Observatory, NRC, FEMA, NYC Building Code archives
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