A visual guide to the earthquake felt in the Philly region
Around 10:23 a.m., a 4.8-magnitude earthquake struck near Tewksbury, N.J. Here’s what happened.
Where did it happen?
Around 10:23 a.m., a magnitude 4.8 earthquake struck near Tewksbury in northern New Jersey. According to the U.S. Geological Survey (USGS), the earthquake’s epicenter was about 70 miles northeast of Philadelphia and 44 miles west of Newark, N.J.
Where did the earthquake originate?
It’s hard to say. According to the USGS, earthquakes occur deeper than our current mapping of the fault line system, so it can be hard to link the two. The nearest major fault to the epicenter is the Ramapo fault line which runs from southeastern New York to Southeastern Pennsylvania.
Where was it felt?
The USGS received reports of weak to light shaking and vibrations similar to a passing truck across Philadelphia, according to the USGS Did You Feel It survey. Residents closer to the epicenter experienced severe shaking – the kind that rattles mounted picture frames and knocks objects off of shelves. There were also reports that people felt it as far as Montpelier, Vt., and Washington, D.C.
Has this happened before?
This was the strongest earthquake in the area in the century. In the last two decades there have only been 18 other earthquakes with a magnitude greater than 2.5 near Philadelphia. Events of this magnitude are rare for this area but worldwide, they are fairly common, happening between 10,000 and 15,000 times per year.
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Methodology
The Inquirer used the U.S. Geological Survey’s Earthquake Hazards Program data.
An earthquake’s magnitude is based on the moment magnitude scale, where a magnitude above 2.5 means that the event was felt.
The USGS uses the Modified Mercalli Intensity (MMI) scale to describe the felt effects of an earthquake. The scale ranges from I to X; the lower numbers typically describe how people experienced the earthquake, but the higher numbers are based on “observed structural damage”.
Staff Contributors
- Design, Development, and Reporting: Charmaine Runes, Jasen Lo, Dain Saint, Sam Morris
- Editing: Sam Morris and Diane Mastrull
- Additional data: John Duchneskie
- Digital Editing: Patricia Madej
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