This is the Biggest and Most Damaging Earthquake in Pennsylvania’s History


Pennsylvania isn’t known for having a lot of earthquakes, but the state has had some big ones in the past. The biggest one ever happened in the northwest of the state on September 28, 1998, close to Pymatuning Lake.

The quake was 5.2 on the Richter scale, and millions of people in several states and Canada felt it. Some buildings and roads were slightly damaged, but no one was hurt or killed.

Pennsylvania’s Seismic History

Pennsylvania has a low to moderate seismic risk, which means that tremors don’t happen very often and are generally small. The state is in a secure continental area of the North American plate, which is a long way from the active plate borders, which are where most earthquakes happen.

However, the state is crossed by a number of old faults and rift zones that can sometimes cause earthquakes.

In 1724, close to Philadelphia, Pennsylvania had its first known earthquake. Since then, the state has been hit by more than 500 earthquakes, most of which were smaller than 3.0 on the Richter scale. Before 1998, Pennsylvania had two earthquakes that were bigger than 6.0 on the Richter scale.

The first happened near Lancaster in 1973, and the second happened near Reading in 1994. Both of these quakes were felt over a large area and did little damage.

Pymatuning Earthquake of 1998

The 1998 Pymatuning earthquake happened because of a crack in the Precambrian basement rocks that lie below most of Pennsylvania. About 5 kilometers (3 miles) deep, the quake’s center was about 24 kilometers (15 miles) southwest of Jamestown, Pennsylvania.

People in Toronto, Canada, and Washington, D.C., among other places, felt the quake. It was followed by several aftershocks, the strongest of which was 8.5 on the Richter scale.

A lot of people lost power, walls and supports cracked, and towers and brick facades fell off. Some companies and schools had to close, and some roads and bridges were shut down for inspection.

In some places, the earthquake also caused landslides, rockfalls, and flooding. The loss was thought to be $3 million altogether.

Pennsylvania’s Future Seismic Risk

The U.S. Geological Survey says that there is a small but not zero chance that Pennsylvania will have a severe earthquake in the next 50 years.

A mild quake with a magnitude of 4.0 to 5.0 is most likely to happen. This kind of quake could do some damage and be felt by many people. A big quake with a magnitude of 6.0 or higher would be the worst thing that could happen.

It could do a lot of damage and hurt a lot of people, but it’s not likely to happen. Pennsylvania’s seismic risk may also be affected by things that people do, like mining, fracking, and building dams. These things can cause earthquakes by changing the stress and fluid pressure in the ground.

However, the link between these things and earthquakes is complicated and not well-known. Also, the earthquakes that are caused are generally small and not dangerous.


In conclusion, Pennsylvania is not usually thought of as a place where earthquakes happen, but it has had some big ones in the past, like the famous Pymatuning earthquake in 1998.

People in the state have a low to high risk of earthquakes, but old faults and rift zones have caused earthquakes in the past.

Even though it’s not likely that there will be a big earthquake in the next 50 years, the damage that could happen, especially because of things people do like mining and fracking, is still a worry. This shows how important it is to keep researching and getting ready.

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