Earthquake Rattles Northwest Pennsylvania


Pleasantville, Pa. – A small earthquake has been recorded 68 miles northeast of Youngstown.

The Lamont Doherty Cooperative Seismographic Network reported a 2.2 magnitude tremor at around 6:30 a.m. between Titusville, Pennsylvania and Allegheny National Forest in Venango County.

Greg Knupp is a firefighter in the town of Pleasantville, Pa, which is less than three miles from the center of the quake which is in a rural, farmland area.

He tells 21 news that he did not feel any shaking, and hasn’t heard reports from anyone else who felt the tremor.

According to the U.S. Geological Survey, which keeps tracks of earthquakes worldwide, most humans do not feel seismic activity between the magnitudes of 1.0 and 3.0, except under special circumstances.

On December 31, 2011, a 4.0 magnitude earthquake was reported in Youngstown. Some research linked that tremor to a class II brine injection well which was closed as a result.

According to the USGS, the largest earthquake (magnitude 4.8) caused damage in 1986 in northeastern Ohio, and the most recent damaging shock (magnitude 4.5) occurred in 1998 at the seismic zone’s eastern edge in northwestern Pennsylvania. Earthquakes too small to cause damage are felt two or three times per decade.

Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast.

A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi).

Earthquakes everywhere occur on faults within bedrock, usually miles deep. Most of the seismic zone’s bedrock was formed as several generations of mountains rose and were eroded down again over the last billion or more years.

At well-studied plate boundaries like the San Andreas Fault system in California, often scientists can determine the name of the specific fault that is responsible for an earthquake. In contrast, east of the Rocky Mountains this is rarely the case.

The Northeast Ohio seismic zone is far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea. The seismic zone is laced with known faults but numerous smaller or deeply buried faults remain undetected.

Even the known faults are poorly located at earthquake depths. Accordingly, few, if any, earthquakes in the seismic zone can be linked to named faults. It is difficult to determine if a known fault is still active and could slip and cause an earthquake.

As in most other areas east of the Rockies, the best guide to earthquake hazards in the Northeast Ohio seismic zone is the earthquakes themselves.

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