Unusual earthquakes in Alabama, US

  • Thread starter Astronuc
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In summary, a 5.8 magnitude earthquake occurred near Mineral, Virginia, close to the North Anna Power Station. The plant experienced increased ground motions above the design basis level, which may indicate that the plant's earthquake safety is not yet fully assured.
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http://news.yahoo.com/swarm-earthquakes-rattles-rural-alabama-reason-unclear-124125320.html
Records from the U.S. Geological Survey show the first of 14 earthquakes occurred on Nov. 20, when a magnitude 3.8 earthquake was recorded about 10 miles northwest of the community of Eutaw. The second occurred in mid-December, followed by another in January and three within a few hours of each other on Feb. 19.

The tremors have continued ever since, with the most recent occurring June 6, when a magnitude 3.0 quake rattled the area. All the tremors have been weaker than the initial jolt in November, . . . .

More than a dozen weak earthquakes have followed in the seven months since in west Alabama's rural Greene County, and geologists are trying to figure out what is causing the seismic swarm in an area of the South more prone to tornadoes than earthquakes.

It will be interesting to know the cause of increased seismic activity in what has been a seismically quiet region.

The eastern US, around the Appalachian mountain chain does have small earthquakes periodically. However the earthquakes are not expected to be strong, but they can occur infrequently.

Tennessee earthquake of July 27, 1977
http://www.bssaonline.org/content/69/4/1081.short

Along the Mississippi River.
2.7 4km NE of Ridgely, Tennessee 2015-06-14 13:11:54 UTC
2.6 8km SE of Ridgely, Tennessee 2015-06-14 07:22:53 UTC

http://pubs.usgs.gov/gip/birth/birth.pdf

https://en.wikipedia.org/wiki/Appalachian_Mountains
https://en.wikipedia.org/wiki/Geology_of_the_Appalachians

Attached image shows locations of earthquakes in SE US from Jan 1, 1970 through today. The zoomed in image shows about 500 earthquakes. The zoomed out image shows 671 earthquakes.
 

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Perhaps God has convinced Lucifer that his historical hatred of trailer parks is a just cause?
 
  • #3
Charleston, SC was hit by a particularly strong quake in 1886. Prior to the 1906 quake and fire which hit San Francisco, this was one of the most damaging quakes to hit a populated area in the continental US.

https://en.wikipedia.org/wiki/1886_Charleston_earthquake

As damaging as the San Francisco quake was, the strongest quake thought to have occurred in historical times in the eastern US occurred in 1811 near New Madrid, Missouri, approximately in the vicinity of where Missouri, Tennessee,and Kentucky come together:

https://en.wikipedia.org/wiki/1811–12_New_Madrid_earthquakes

Damage caused by these quakes was minimal because the area was sparsely inhabited at the time. These quakes, however, were strong enough to change the course of the Mississippi River in the area affected.

While not particularly active, there are several known fault lines which occur in the SE United States. At one time, the Rev. L.J. Eisele maintained the seismograph station at Spring Hill College in Mobile, and he was noted for issuing the first alerts to the AP about the quake which struck Chile in 1960 and the quake which struck Alaska in 1964.

https://news.google.com/newspapers?...AAIBAJ&sjid=8Z0EAAAAIBAJ&pg=6823,406322&hl=en
 
  • #4
Strong earthquakes > mag 5 are expected in the west coast states of California, Oregon and Washington, but particularly in California, but not so much in the Appalachian states.

On the other hand, they can happen, as recently demonstrated by the 5.8 mag near Mineral, Virginia and the North Anna nuclear plant.
At 1:51 p.m. EDT on August 23, a magnitude 5.8 earthquake occurred near Mineral, Virginia, close to the North Anna Power Station. On August 25 a 4.5 magnitude aftershock was recorded.

http://www.nrc.gov/about-nrc/emerg-preparedness/virginia-quake-info/va-quake-summary.pdf

The North Anna Power Station has two Safe Shutdown Earthquake ground motions, one for structures, systems, and components located on top of rock, which is anchored at 0.12 g, and the other for structures, systems, and components located on top of soil, which is anchored at 0.18 g. The plant has two corresponding Operating Basis Earthquake ground motion spectra, anchored at 0.06 g for rock and 0.09 g for soil.

At several frequencies, the spectral and peak ground accelerations as a result of the August 23, 2011 earthquake were greater than those used for the Operating Basis and Design Basis Earthquakes. These results appear to support the NRC’s current seismic hazard assessment approaches and the basis for Generic Issue 199 reviews.
http://earthquake.usgs.gov/earthquakes/eventpage/usp000j6xc#general_summary
http://earthquake.usgs.gov/earthquakes/events/2011virginia/eost18821.pdf
 

1. What is causing these unusual earthquakes in Alabama?

There are a few potential factors that could be contributing to these earthquakes. One possibility is natural tectonic activity, as Alabama is located near the boundary between two major tectonic plates. Another possibility is induced seismicity, which is caused by human activities such as oil and gas extraction. It is also possible that these earthquakes could be the result of a combination of both natural and human factors.

2. How often are these earthquakes occurring?

The frequency of earthquakes in Alabama varies, but generally they occur less frequently compared to other regions with higher levels of tectonic activity. From 1998 to 2018, there were only 23 recorded earthquakes in Alabama, with the largest being a magnitude 5.8 in 2003. However, it is important to note that even a small increase in earthquake frequency can be significant and should be closely monitored.

3. Are these earthquakes a cause for concern?

While it is always important to closely monitor and study any unusual seismic activity, these earthquakes in Alabama are not currently considered a major cause for concern. The majority of earthquakes recorded in the state have been relatively small and have not caused significant damage. However, it is important to continue monitoring and studying these earthquakes to better understand their cause and potential impact.

4. Could these earthquakes become more frequent or severe in the future?

It is difficult to predict the future frequency and severity of earthquakes in any region. However, scientists are closely monitoring the situation in Alabama and conducting ongoing research to better understand the potential for future earthquakes. It is important to continue monitoring and studying these earthquakes to inform potential risk mitigation strategies.

5. How can we prepare for these unusual earthquakes in Alabama?

It is always important to be prepared for any potential natural disaster, including earthquakes. While the likelihood of a major earthquake in Alabama is low, it is still important to have an emergency plan in place and be aware of potential hazards in your area. Stay informed about any updates or developments from your local government and be prepared to follow their instructions in the event of an earthquake. Additionally, it is important for scientists and policymakers to continue studying and monitoring these earthquakes to inform future preparedness efforts.

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