This is a brief summary of all the earthquakes that have occurred in Pennsylvania. The information is from the United States Geological Survey or USGS. Though the Ramapo Fault Line does run up through eastern Pennsylvania into New Jersey, it is not considered a major fault line and it is relatively inactive. So there are really no major fault lines in Pennsylvania.
The early history of earthquakes in Pennsylvania is spotty at best. In the years 1737, 1758, 1783, and 1791, the USGS reports that earthquakes outside of Pennsylvania caused large tremors in the state.
On March 17 and November 29, 1800, two earthquakes the USGS reports as severe rocked the Philadelphia area. On November 11 and 14, 1840, two earthquakes struck in the Philadelphia area that caused large swells on the Delaware River alongside the city.
On May 31, 1884, Allentown was rocked by an earthquake that caused dishes to be thrown from tables. On August 10, 1884, towns and cities in eastern Pennsylvania felt the effects of a large earthquake that struck near New York City. From that point on, the records of earthquakes in Pennsylvania are better recorded.
Image Sourceby Douglas Muth (People evacuating Downtown Philadelphia office building during August 23, 2011 earthquake)
March 8, 1889: a 10 second tremor was felt from a intensity V earthquake in towns around Harrisburg, Reading and York.
May 31, 1908: a intensity VI earthquake was felt in the Allentown area that took down some chimneys.
October 29, 1934: an intensity V earthquake struck the Erie, Pennsylvania area that caused buildings to sway and threw dishes from tables.
July 15, 1938: an intensity VI earthquake struck in southern Blair County that caused plaster to fall from walls and dishes to be broken in Henrietta and Clover Creek. Some people reported that their wells were affected by the earthquake in Clover Creek.
January 7, 1954: an intensity VI earthquake struck west of Reading around the town of Sinking Spring. Dishes and bottles were broken, furniture was moved and plaster came off of walls. For the rest of January 1954, residents of Sinking Spring experienced a number of minor tremors or shocks.
February 21, 1954: roughly $1 million in damage occurred in Wilkes-Barre, Pennsylvania when parts of the city sunk to lower levels causing gas and water main breaks, sidewalks to collapse, and buildings walls and cellars to crack. Two days later, further damaged was caused by another disturbance in the same area. It's unclear if the damage was caused by an earthquake that caused an underground coal mine under the city to collapse, or whether the damage was just as a result of subsidence in the coal mine.
September 14, 1961: an intensity V earthquake struck in the Lehigh Valley area that caused buildings to sway and a chimney to fall over in Allentown.
December 27, 1961: an intensity V earthquake struck northeast Philadelphia and the surrounding suburbs that caused buildings to shake and moved dishes and other objects on tables.
May 12, 1964: a 4.5 magnitude earthquake struck near Cornwall, Pennsylvania, causing a cracked wall and falling plaster. Underground iron mine workers in the area reported feeling a very severe jarring motion from the quake.
December 10, 1968: a 2.5 magnitude earthquake struck in New Jersey across the Delaware River causing trembling and shocks in Darby and Philadelphia. Toll booth workers on the Benjamin Franklin and Walt Whitman Bridges in Philadelphia reported that their toll booth trembled from the earthquake.
December 7, 1972: an intensity V earthquake struck in the New Holland, Pennsylvania area. Effects were felt in both Berks and Lancaster counties in the state.
April 23, 1984: a 4.4 magnitude earthquake struck in Lancaster County centered near Marticville. The quake caused minor damage like cracked windows, plaster falling off walls, and basement foundations to crack. The area had a forewarning of the earthquake when a foreshock occurred on April 18, 1984.
January 16, 1994: a 4.0 magnitude earthquake struck in the Reading area at 12:42 am.
January 16, 1994: a 4.6 magnitude earthquake also struck in the Reading area at 1:49 am, that was felt in Baltimore, New York City, and as far away as Toronto, Canada.
September 25, 1998: a 5.2 magnitude earthquake struck near Meadville in northwestern Pennsylvania. The quake was felt all over northern Ohio, northern Indiana, southeastern Michigan, in parts of West Virginia, Illinois, New Jersey and southern Ontario Province in Canada.
August 23, 2011: a 5.8 magnitude earthquake struck in central Virginia near the town of Mineral that was felt throughout most of Pennsylvania. This earthquake did not occur in Pennsylvania, but was felt throughout most of the state.
For more see Largest Earthqaukes in New York City History
Largest Earthquakes in World History