What is an Earthquake Swarm? - The United States Geological Survey has reported a large number of earthquakes in central Arkansas with the largest quake thus far -- a 4.7 temblor -- occurring on Monday.
This earthquake is the largest to hit the state in the last 35 years and understandably has nerves on edge. The earthquakes in Arkansas are being called an earthquake swarm. The term may sound ominous, but it is not difficult to understand. What exactly is an earthquake swarm and what does it mean for the areas a swarm occurs in?
What is an Earthquake Swarm?
An earthquake swarm is a series of small earthquakes that occur in close proximity to each other over a period of time. The USGS defines such an event as "as clusters of earthquakes closely spaced in time and area that do not have a defined mainshock."
The area around the Mount St. Helen's volcano experiences earthquake swarms -- most recently during January and February, causing the USGS to continue watching the area closely.
In 2004, there was a large swarm at Yellowstone National Park raising concerns about the Yellowstone caldera volcano. That particular swarm saw about 400 seismic events registered over a three-day period of time -- with magnitudes ranging between 0 and 2.7.
Earthquake Swarms in Arkansas
In Arkansas, an earthquake swarm occurring near the towns of Greenbrier and Guy has been ongoing since last year. Both towns are located within a few miles of each other, just north of Little Rock.
According to the USGS website, scientists have no real answer for why earthquake swarms begin or how long they can be expected to last. The swarms in Arkansas have been going on since August 2010 and have recently increased in activity, with Monday's quake being the largest earthquake Arkansas has experienced in 35 years. This 4.7 quake was felt in Missouri, Tennessee, Oklahoma and Mississippi.
This series of earthquakes is not the first in Arkansas as a swarm known as the Enola swarm occurred in 1982 -- starting with a 1.2 quake on Jan. 12. That area saw about 40,000 earthquakes and microquakes with 93 of them large enough to be felt by residents. The largest quake in the Enola swarm was a 4.5 quake and the most recent earthquake associated with that swarm was recorded in 2006. Enola is within about 20 miles of Guy and Greenbrier.
Does an Earthquake Swarm Mean a Larger Quake is Coming?
Not necessarily, according to the USGS. In the instance of swarms occurring near a volcano such as Mount St. Helen's or Yellowstone, the small quakes could mean the volcano is becoming restless and there is potential for an eruption. In an area such as Arkansas where there is no volcanic activity, the swarms do not mean a bigger quake is on the horizon.
The USGS website news release regarding the Arkansas earthquake swarms states that "The possibility of a larger earthquake cannot be discounted, but none of the other swarms have caused any reason to expect a future earthquake large enough to cause significant damage in central Arkansas."
Are the Arkansas Swarm Earthquakes Related to the New Madrid Seismic Zone?
Logistically, the epicenter of the current rash of earthquakes is outside of the New Madrid Seismic Zone, which runs from Cairo, Ill. southwest to Marked Tree, Ark. Marked Tree is about 200 miles northeast of the current quake epicenters. A large earthquake within the NMSZ would affect the area currently experiencing earthquakes, though.
Natural gas injection wells have been suggested as being a cause for the seismic disturbances in the region but that has not been confirmed or discounted in relation to the swarms.
A recent Associated Press report stated that residents in the Arkansas swarm area have begun to see minor damage to structures and property due to the ongoing quakes as scientists continue to look for answers. ( news.yahoo.com )
This earthquake is the largest to hit the state in the last 35 years and understandably has nerves on edge. The earthquakes in Arkansas are being called an earthquake swarm. The term may sound ominous, but it is not difficult to understand. What exactly is an earthquake swarm and what does it mean for the areas a swarm occurs in?
What is an Earthquake Swarm?
An earthquake swarm is a series of small earthquakes that occur in close proximity to each other over a period of time. The USGS defines such an event as "as clusters of earthquakes closely spaced in time and area that do not have a defined mainshock."
The area around the Mount St. Helen's volcano experiences earthquake swarms -- most recently during January and February, causing the USGS to continue watching the area closely.
In 2004, there was a large swarm at Yellowstone National Park raising concerns about the Yellowstone caldera volcano. That particular swarm saw about 400 seismic events registered over a three-day period of time -- with magnitudes ranging between 0 and 2.7.
Earthquake Swarms in Arkansas
In Arkansas, an earthquake swarm occurring near the towns of Greenbrier and Guy has been ongoing since last year. Both towns are located within a few miles of each other, just north of Little Rock.
According to the USGS website, scientists have no real answer for why earthquake swarms begin or how long they can be expected to last. The swarms in Arkansas have been going on since August 2010 and have recently increased in activity, with Monday's quake being the largest earthquake Arkansas has experienced in 35 years. This 4.7 quake was felt in Missouri, Tennessee, Oklahoma and Mississippi.
This series of earthquakes is not the first in Arkansas as a swarm known as the Enola swarm occurred in 1982 -- starting with a 1.2 quake on Jan. 12. That area saw about 40,000 earthquakes and microquakes with 93 of them large enough to be felt by residents. The largest quake in the Enola swarm was a 4.5 quake and the most recent earthquake associated with that swarm was recorded in 2006. Enola is within about 20 miles of Guy and Greenbrier.
Does an Earthquake Swarm Mean a Larger Quake is Coming?
Not necessarily, according to the USGS. In the instance of swarms occurring near a volcano such as Mount St. Helen's or Yellowstone, the small quakes could mean the volcano is becoming restless and there is potential for an eruption. In an area such as Arkansas where there is no volcanic activity, the swarms do not mean a bigger quake is on the horizon.
The USGS website news release regarding the Arkansas earthquake swarms states that "The possibility of a larger earthquake cannot be discounted, but none of the other swarms have caused any reason to expect a future earthquake large enough to cause significant damage in central Arkansas."
Are the Arkansas Swarm Earthquakes Related to the New Madrid Seismic Zone?
Logistically, the epicenter of the current rash of earthquakes is outside of the New Madrid Seismic Zone, which runs from Cairo, Ill. southwest to Marked Tree, Ark. Marked Tree is about 200 miles northeast of the current quake epicenters. A large earthquake within the NMSZ would affect the area currently experiencing earthquakes, though.
Natural gas injection wells have been suggested as being a cause for the seismic disturbances in the region but that has not been confirmed or discounted in relation to the swarms.
A recent Associated Press report stated that residents in the Arkansas swarm area have begun to see minor damage to structures and property due to the ongoing quakes as scientists continue to look for answers. ( news.yahoo.com )
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