March 14, 2010

Earthquakes in (Southwestern) Pennsylvania



     Pennsylvania: the Quaker state.

     Earthquakes shaking Southwestern Pennsylvania? Is this the source of its second most common nickname, the Quaker State?

     One of the above statements is true: earthquakes do occur in Southwestern Pennsylvania. However, the nickname “Quaker State” originates from the fact that the state’s founder, William Penn, belonged to a religious sect known as Quakers.

     Although earthquakes occur far less frequently in Southwestern Pennsylvania than they do in California, they do occur. Forty-five earthquakes have been recorded in Pennsylvania since 1900,*** some originating in the east, others in the west.

     Eastern originating earthquakes include an 1889 event epicentered in York, Pennsylvania. The majority of the residents of Harrisburg and other Pennsylvania cities who experienced this earthquake were naïve to this natural disaster. A newspaper report stated that “”The whole city and it’s suburbs were shaken, houses tumbled, and heavy articles swayed while dishes were shaken off the supper tables, stoves rattled, and in fact so great was the disturbance that many people were nearly crazed with fear. Women ran shrieking from their houses with their infants in their arms and strong men blanched with terror”

     On February 10, 2005, a barely notable earthquake occurred in Crawford County at the north end of Conneaut Lake, the same general region where a 5.2 magnitude earthquake occurred on September 25, 1998.****

      Earthquakes in 1901 near Portsmouth (Scioto County), in 1926 near Pomeroy (Meigs County), Two earthquakes shook western Ohio and the surrounding states, including western Pennsylvania, in 1937—one on March 2, the other on March 9.The shocks lasted two to three minutes each. A January 31, 1986, 5.0 magnitude earthquake, epicentered in the area of Lake and Geauga Counties, Ohio, was felt in ten other states and southern Canada. (6)

     Ohio is located on the periphery of the New Madrid Seismic Zone, an area in Missouri and adjacent states, the location of the largest earthquake sequence occurred in the continental United States—four earthquakes in 1811 and 1812. The estimated 8.0 earthquake toppled chimneys in Cincinnati. ******(6)
     The state of  Pennsylvania has two seismically active zones, one east in Lancaster and the other northwest near Lake Erie.** The closest plate boundary to the East Coast is the Mid-Atlantic Ridge, which is approximately 2,000 miles to the east of Pennsylvania.

     Predicting large earthquakes in Pennsylvania is difficult due to the long spans of time between events. Furthermore, severity can be ten times more than those of equal magnitude earthquake in California, because the region is based on relatively brittle, flat-lying sedimentary rocks that tend to carry the earthquake waves over a much larger area.******(6)
     Because earthquakes are so infrequent in Pennsylvania and they are generally mild events, residents don’t take precautions, such as bolting bookcases to the wall, strapping water heaters to the wall, or maintaining an emergency supply of canned food and water. However, geologists cannot guarantee that the state will not experience an earthquake in the magnitude of five or six on the Richter Scale.



To receive notification of each new post on Carolyn’s Compositions, subscribe by typing your e-mail address in the SUBSCRIPTION box in the upper right hand column of this page. Notification will begin after you CONFIRM your subscription in an e-mail sent to you by wordpress for that purpose.


I welcome any comments you might have on this or any other CAROLYN’S COMPOSITIONS posts. Use the COMMENT box below to respond. For details on the COMMENT CONTEST click on:



A Chilean’s Thoughts on the Chilean Earthquake


The Partners in Progress Mission Project in Haiti

Mosquito Nets Fight Malaria in Africa

Mad Hatters, Johnny Depp, and Alice in Wonderland

Leave a Comment »

No comments yet.

RSS feed for comments on this post. TrackBack URI

What is your opinion?

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Blog at

%d bloggers like this: