Time to "edumacate" ourselves about earthquakes & Pennsylvania

[Divernan]

Now that both Arkansas and Texas have documented the relationship of fracking to increased earthquake activity (in a part of Texas, for example, which had not had any quakes for at least 146 years), I began to so some research on earthquakes and Pennsylvania. For starters, here's a nice, calm, overview article from the Lehigh Earth Observatory. I converted a few comments to ALL CAPS for added emphasis. The key concept is "intraplate sesimicity". There WILL be a quiz!

http://www.leo.lehigh.edu/projects/seismic/pennquakes.html

snips:

The closest plate boundary to the East Coast is the Mid-Atlantic Ridge, which is approximately 2,000 miles to the east of Pennsylvania. However, 200 million years ago when the continent Pangaead rifted apart forming the Atlantic Ocean, the north eastern coast of America was at a plate boundary. Being at the plate boundary many faults were formed in the region. Although these faults are geologically old and are contained in a passive margin, they act as pre-existing planes of weakness and concentrated strain. When a strain exceeds the strength of the ancient fault, it ruptures causing an earthquake.EARTHQUAKES CAN ALSO BE INDUCED THROUGH HUMAN ACTIVITIES SUCH AS MINING AND INJECTION OR PUMPING OF GROUNDWATER. The 1994 earthquake in Reading is just a reminder that there is still a possibility of an earthquake in Pennsylvania. Along with this piece are some articles and descriptions of earthquakes in Pennsylvania occurring in the 18th, 19th, and 20th centuries.

Link to USGS earthquake history 1737-1973

Earthquakes that occur far from plate boundaries are considered intraplate earthquakes.PENNSYLVANIA EARTHQUAKES ARE INTRAPLATE EARTHQUAKES because the closest plate boundary, the Mid-Atlantic Ridge, is over 2000 miles away. The spreading of the Mid-Atlantic Ridge causes stress and strain. This stress and strain is also put on the older fault such as the Paleozoic collisional thrust faults and the mesozoic extensional faults. During the Jurassic, the main trend of the faults formed were North-South, parallel to the opening of the Atlantic Ocean. Since then, the faults are more or less perpendicular to the current state of stress. This may be the cause of the INTRAPLATE SEISMICITY. These faults are still subject to stress and strain which may reactivate older faults causing seismicity.

Maps of Pennsylvania seismicity from 1798 to present

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. The Lancaster zone is the most active of the two due to the Paleozoic thrust sheets and the Newark extensional basin. The largest earthquake that occured in the Lancaster zone registered 4.6 on the Richter Scale. Little is known or understood about these zones; our seismometer will help us understand more. The Lancaster seismic zone includes areas around Lancaster, Reading, and Allentown.

Intraplate Seismicity

An intraplate seismic zone lies on the inner part of the tectonic plate. Most earthquakes occur where two plates meet each other, the plate boundary. However, earthquakes can and do occur at faults within the plate itself. In eastern North America there are three large intraplate areas that have been seismically active; the Mississippi Valley near the town of New Madrid, Missouri; the St. Lawrence Valley in eastern Canada; and Charelston, South Carolina. All of these places were once an mid-continental rift zone creating extensional faults. These regions have experienced earthquakes of magnitude 7 on the Richter scale. Hazard rates for intraplate earthquakes are significantly less to none when compared to the more active plate boundary areas. However, an earthquake in an intraplate area can cause considerable damage, particularly in the Eastern United States. MANY OF THE ROCKS IN PENNSYLVANIA ARE OLD, CRYTALLINE, AND FRACTURED. When a magnitude 4 or 5 earthquake strikes Pennsylvania, the ENERGY from the earthquake is transferred MUCH QUICKER AND FARTHER than in the Western United States. AN EARTHQUAKE THAT CAUSES LITTLE DAMAGE IN CALIFORNIA, OREGON OR WASHINGTON MAY CAUSE CONSIDERABLY MORE DAMAGE IN THE EASTERN U.S.

[Divernan]

1. Lehigh Earth Observatory; Apparently NOT funded by Big Oil

So you won't see any scientists from this place on Corbett's Marcellus Shale Advisory Commission!

http://www.leo.lehigh.edu/projects/seismic/index.html

LEO Seismic Station
Earthquakes and volcanoes are constant reminders that we live on a dynamic planet. Earthquakes cause millions of dollars in damage and tragic loss of life, yet they also provide key insights into earth structure and active tectonic processes. Seismology is a quantitative discipline that records and studies the generation and propagation of elastic energy in the earth. Studying earthquakes is important for understanding seismic hazards in urban areas and developing appropriate responses. Seismic networks and arrays are the primary tools used to monitor compliance with the Nuclear Test Ban Treaty. Earthquakes are also essential to understanding motion and deformation of the earth's crust and mantle.

We have established a broadband seismic station on South Mountain, Lehigh University, to monitor local, regional, and global seismic activity. Data collected from the seismic station provides information on active seismicity in northeastern Pennsylvania, including the Lancaster Seismic Zone and the Reading Earthquake Sequence. Our station is a part of the Northeastern Regional Seismic Network, which monitors earthquake activity in the eastern U.S. The information collected links to the GSN (Global Seismic Network) maintained and operated jointly by IRIS (Incorporated Research Institutes in Seismology) and the US Geological Survey.Lehigh University is an IRIS member

Students participated in all aspects of this project, from the initial planning stage including site evaluation and selection to the installation and development phase. Since the station is up and running, students maintain and operate the seismic station on a day-to-day basis, analyze earthquake data, and serve as a resource in the Lehigh Valley and Eastern Pennsylvania for information about earthquakes locally as well as globally. A student list has been compiled and contains the names of all interns who worked on LEO's seismic station.

[Divernan]

2. 1889 earthquake less than 25 miles from TMI.

The OP link includes a description of an 1889 earthquake centered in York, PA, which is less than 25 miles from TMI.

"Here are some descriptions of an earthquake felt in Harrisburg and other Pennsylvania cities on March 8, 1889. Although some people were aware of what an earthquake was in the year 1889, the majority of people were naïve 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.

A York dispatch reported that the most severe shock of this particular earthquake was felt at 6:40 p.m. 2 "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."

Anyone know if fracking activities are occurring, or are in the planning stage, in proximity to the following Pennsylvania nuclear plants

http://www.eia.doe.gov/cneaf/nuclear/state_profiles/pennsylvania/pa.html

State Overview

There are five operating nuclear power plants in Pennsylvania:

Beaver Valley in Beaver County
* In 2006, First Energy replaced the facility's three steam generators and a reactor vessel.
* On November 5, 2009, the Nuclear Regulatory Commission (NRC) approved a 20-year license renewal for Beaver Valley units 1 and 2.

Limerick in Montgomery County
* The containment type is Mark 2.
* Exelon operates four of the seven licensed Mark 2 BWRs: two each at LaSalle, Illinois, and Limerick, Pennsylvania. (The others in service are the lone reactor at Columbia in Washington and the pair at Nine Mile Point in New York.)

Peach Bottom (Units 2 and 3) in York County
* Philadelphia Electric ordered Peach Bottom Unit 1 in 1958. Unit 1 was a 40-megawatt experimental High Temperature Helium-Cooled and Graphite-moderated reactor that was permanently shut down in 1974. Peach Bottom 2 and Peach Bottom 3 are still in service.

Susquehanna (units 2 and 3) in Luzerne County
* The Susquehanna nuclear plant takes its name from the adjacent Susquehanna River.
* As of December 31, 2008, Unit 1 was the largest reactor in Pennsylvania and unit 2 was the second largest.
* Susquehanna's reactors are relatively new, but on November 24, 2009, the owners received a 20-year license extension for both reactors from the Nuclear Regulatory Commission.
* No additional reactors are planned at the Susquehanna plant itself; however, construction of a new reactor is contemplated at Bell Bend, a property adjacent to the Susquehanna site. More information on the Bell Bend project is available in the Status of Potential New Commercial Reactors in the United States.

Three Mile Island Unit 1 in Dauphin County
* Three Mile Island may be the most widely known nuclear power plant in the United States due to an accident to its number 2 reactor in March 1979. A combination of equipment malfunctions and human error led to a loss of coolant which damaged the reactor core. The reactor was permanently shut down following the accident. The lessons learned from Three Mile Island, however, resulted in enhancements in training, safety procedures, emergency response, and oversight.