Chart of Earthquakes occurring in or affecting PA_The RockDoctor. SW PA Geology and Geography. Washington County PA 'Little Washington' Research and Education

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to Geology and Geography in SW Pennsylvania

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 Rocks, Minerals, Geology, and Geography 
of SW Pennsylvania
Chart of Earthquakes occurring in or affecting PA

Chart of Earthquakes occurring in or affecting PA.

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The most Seismically active areas in Pennsylvania

In Pennsylvania there are two seismically active zones. One is located in Lancaster while another zone is in the northwestern part of the state by Lake Erie.

Plateau and the true Appalachian Mountains in Pennsylvania

Earthquake epicenters in Pennsylvania with Landforms 1798 to present

Table of Earthquakes affecting Pennsylvania made from information on USGS Pennsylvania Earthquake page.

Date Fault location Magnitude Cities in PA affected Articles for Further Reading
pre-1737 No records made.   --- ---
1663  centered 
in St. Lawrence River region
"Very severe" may have been felt in PA  
1727 Newbury, Massachusetts "damaging" "probably" affected  PA  
December 18, 1737 New York City ? "strong" felt in Massachusetts, Pennsylvania,  Delaware.   
1758 origins outside the State      
1783 origins outside the State      
1791 origins outside the State      
March 17, 1800 at Philadelphia "severe"     
November 29, 1800 at Philadelphia "severe"    
December 16, 1811 (two within 6 hours) 
epicenter in northeast Arkansas felt strongly for 130,000 square kilometers (50,000 square miles); moderately across nearly 3 million square kilometers (1 million square miles) 1st - 2:15 a.m.
M ~7.2  8.1

2nd 8:15 a.m.; 
M ~7.28.1

January 23, 1812, New Madrid North Fault in the Missouri Bootheel      
February 7, 1812 with numerous aftershocks New Madrid, Missouri Territory (Reelfoot Fault)   (4:45 a.m.); 
M ~7.48.0

Aftershocks went on for almost 6 months

November 11, 1840 at Philadelphia PA      
November 14, 1840 at Philadelphia PA      
August 17, 1873 epicenter at Sharon, Mercer County, PA   small earthquake: Modified Mercalli intensity (MMI) of III  
May 31, 1884 Allentown, PA      
August 10, 1884 centered near New York City      
August 31, 1886 Charleston, South Carolina  felt in most of Pennsylvania estimated magnitude  around 7.5 Intensity reached X  
March 8, 1889   Harrisburg, Philadelphia, Reading, York, and other towns in that area.    
May 31, 1908, Allentown, PA less than  150 square kilometers from Allentown    
October 29, 1934 felt at Erie PA mostly localized intensity V   
November 1, 1935  epicenter near Timiskaming, Ontario (northwest of the St. Lawrence Seismic Zone proper) lower intensities, throughout PA estimated magnitude 6.4  
August 26, 1936 Greenville, Mercer County, PA   MMI of III  
 July 15, 1938 southern Blair County mostly localized    
February 21, 1954; 2nd one on February 23 Wilkes-Barre mostly localized    
September 14, 1961 Lehigh Valley; Allentown  mostly localized    
December 27, 1961 northeast suburbs of Philadelphia mostly localized    
May 12, 1964 Cornwall  mostly localized magnitude 4.5 (VI)  
December 7, 1972   approximately 1,200 square kilometers of Berks and Lancaster Counties intensity V effects  
April 23, 1984    Lancaster County, PA 4.4 M  
April 14, 1985  Conneaut Lake, Crawford County, PA   magnitude of 3.2 located by instruments  
Jan. 16, 1994 Pennsylvania   4.6M  
September 25, 1998 120 km (75 miles) NNW of Pittsburgh, Pennsylvania. Felt in northern Ohio, most of Pennsylvania; northern Indiana, southeastern Michigan; New York, West Virginia. Felt in parts of Illinois, New Jersey. Also felt in much of southern Ontario, Canada. magnitude 5.2 ; results: old wells went dry; new wells filled; some filled with sulfur and water  * The strongest in PA recorded history.


Mercalli Intensity Earthquake epicenters in Pennsylvania 1798 to present


March 8, 1889. Although some people were aware of what an earthquake was in the year 1889, the majority of people were nave to this natural disaster. The center of this particular earthquake was in York, Pennsylvania. The vibrations extended to Philadelphia to the east, 
Reading to the north, Frederick to the west, and Baltimore to the south.

Pennsylvania earthquakes are intraplate earthquakes because the closest plate boundary, the Mid-Atlantic Ridge, is over 2000 miles away.

Pymatuning Earthquake - The largest recorded Pennsylvania earthquake occurred about 15 miles from Sharon, Northwestern Pennsylvania September 25, 1998. The earthquake measured 5.2 on the Richter scale and was felt over approximately 200,000 square kilometers in the northern United States and southern Canada.

From The Lehigh Earth Observatory LEO



Geologic Time Scale, ES 4 The Geological Story of Pennsylvania, page page C-3

Northeast Ohio and Northwest Pennsylvania Earthquakes

Educational Series 10: Earthquake Hazard in Pennsylvania

Abridged from Earthquake Information Bulletin, Volume 8, Number 4, May - June 1973, by Carl A. von Hake. 

All US Earthquakes from 1568 to 1989

Damaging Earthquake Map 1750 to 1996


Continue Virtual Field Trip Tour - Washington County Pennsylvania Earthquake Effects


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