Most earthquakes are associated with the boundaries of tectonic plates. Pennsylvania, however, is about 2,000 miles west of the closest active boundary, the mid-Atlantic Ridge, which runs down the center of the Atlantic Ocean. However, about 200 million years ago, when the supercontinent Pangea was breaking up and the Atlantic Ocean was first opening, the east coast of North America was an active boundary zone
Northeastern Pennsylvania is a seismically quiet area compared to more active zones along the west coast, such as the San Andreas fault area. However, large quakes from other areas are perhaps occasionally felt here. The great New Madrid, MO, earthquakes of 1811-12 would have shaken our area, as would have the Charleston, SC, quake of 1886. Pennsylvania has several areas that are more seismically active than Northeastern Pennsylvania (NEPA), including the Lancaster, York, Philadelphia, Reading, and Erie areas. The greatest quake recorded in PA was the 5.2 (Richter) tremblor that occurred September 25, 1998, near Pymatuming Reservoir in the northwest part of the state.
Within the Tunkhannock Creek watershed, the only quake in recent times was a 1.8 quiver that had its epicenter at Hop Bottom, Susquehanna County, on August 14, 1982. Three other nearby events were recorded prior to 1970: two in Mill City, Wyoming County (1950, 3.3 magnitude; 1963, 3.4 magnitude), and one in Fleetville, Lackawanna County, in 1940.
None of these, however, had a maximum intensity (according to the Modified Mercalli Intensity Scale) of IV or greater, and hence are considered to be minor. A level IV earthquake would be felt during the day by many indoors, but outdoors by few. Dishes, windows, and doors are disturbed, and walls make creaking sounds.
Scharnberger, C. 1989. Earthquake Hazard in Pennsylvania. Pennsylvania Geologic Survey, 4th series, Educational Series 10, 14p.
Schultz, C. H., ed. 1999. The Geology of Pennsylvania. Pennsylvania Geologic Survey and Pittsburgh Geological Society, Special Publication 1. 888 pp
USGS Earthquake Hazards Program
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