Post by Graveyardbride on Jun 15, 2015 12:00:54 GMT -5
Mysterious Quakes Shake Alabama
EUTAW, Ala. – Jim Sterling didn't know what had hit his 156-year-old antebellum home when an earthquake struck in Greene County, Alabama, early one morning last November. Startled, he grabbed a gun and ran outdoors. In the pre-dawn chill, Sterling said, he found an odd scene: galloping horses, unsettled cattle and barking dogs. "I heard a boom and felt the shaking," Sterling said. "It really upset me."
More than a dozen weak earthquakes have followed in the seven months since in the west central Alabama 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 is interesting that recently there has been more activity there than in the last four decades," said Sandy Ebersole, an earthquake expert with the Geological Survey of Alabama.
Records from the U.S. Geological Survey show the first of 14 earthquakes occurred November 20, 2014, 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 February 19. The tremors have continued, 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, and Ebersole said some have been too slight for residents to detect.
Located about 35 miles from Tuscaloosa, the whole of Greene County has around 8,700 residents and the area where the quakes are occurring is sparsely populated. Farmlands and forests are dotted by hunting preserves and old homes left over from Alabama's past as a cotton-producing state.
Experts have installed a seismic monitor in a field to enable them to obtain better information about the quakes, none of which has caused major damage. Ebersole said researchers are trying to rule out potential causes such as blasting for quarries and sonic booms. They've even held meetings with rattled area residents. The quakes could be linked to underground cracks, or faults, found in the area in recent years at varying depths, Ebersole said. But just what has been causing the ground to shake is unclear.
One potential source that regulators are discounting is hydraulic fracturing or "fracking," a process for extracting underground oil or natural gas that has been blamed for earthquake swarms elsewhere, including Oklahoma. Wastewater is sometimes injected underground, a method the government has blamed for quakes. While Greene County is on the edge of Alabama's primary region for oil and gas production, state geologist Nick Tew said no such production or disposal work is going on in the area where the quakes are occurring.
The mysterious shaking has left residents like Mark McClelland to protect themselves in the only way they can. "After the second or third one, I went to get some earthquake insurance," said McClelland. "It's not bad, about $150 a year."
The hearty construction methods and thick timbers used in his 163-old Greek Revival mansion provide some comfort to Barden Smedberg, who operates the house as a wedding venue and a bed and breakfast. One of the earliest quakes shook loose curtain rods from window frames at his Everhope Plantation (pictured above), he said. But no other damage has occurred. "This house has been here since 1852. I don't think it's going anywhere," said Smedberg. Even without much damage or a major shake to date, Sterling said he would still like to know what is causing the quakes. "A lot of people are wondering what's going on," he said.
According to the Geological Survey of Alabama's website, quakes can and do occur across the state: "Most of the earthquakes we experience in Alabama are associated with the Southern Appalachian Seismic Zone (an extension of the East Tennessee Seismic Zone) that runs along the Appalachian Mountains from the northeastern corner into the central part of the state and the Bahamas Fracture Seismic Zone in southern Alabama." Here's a look at 11 quakes that caused damage in Alabama:
Tremors from Pensacola quake, 1781. According to USGS earthquake records, one of the largest quakes to impact the territory that is now Alabama is estimated to have been a 6 or 7 magnitude quake that occurred just across the state line in Pensacola, Florida, in May of 1781. The Geological Survey of Alabama said there were no deaths but "damage reported included ammunition racks torn from barracks walls and a leveled house in the vicinity."
Tremors from New Madrid Fault quakes, 1811-1812. A major earthquake event occurred when the Alabama Territory was still frontier land, with three 8.0-plus magnitude quakes occurring in 1811 and 1812 along the New Madrid Fault. Although the quakes were centered in Missouri, they were felt in numerous states and caused the earth to shift and form Reelfoot Lake in Tiptonville, Tennessee. The GSA wrote: "These gigantic earthquakes were comparable to the San Francisco shock in 1906 and were felt over 2 million square miles, more than half of the total area of the United States."
Tremors from South Carolina quake, 1886. The impact of a 7.3 magnitude earthquake that struck Charleston, South Carolina, September 1, 1886 shook parts of Alabama enough to cause minor damage. A 1933 photo of the Alexander-Hurt-Whatley house in Tuskegee, built in 1845, shows a large crack in one wall purporting to have been caused by the Charleston quake. The GSA reports that most of the damage was in northern Alabama: "This shock, located about 400 miles east of Alabama's border, caused minor damage in the northeastern part of the state."
Gadsden, 1905. According to a 1975 article in The Gadsden Times, tremors from a January 27, 1905, quake centered on Gadsden, were felt more than 300 miles away. No one was killed. The Earthquake Information Bulletin reported: "At Gadsden, chimneys were thrown down and a well dried up, no water being found 30 feet below the bottom of the well. Aftershocks occurred up to November."
Irondale, 1916. The largest quake to strike Alabama directly was a 5.1 magnitude quake that hit the Irondale-Easonville area October 18, 1916. The GSA reported: "Near the epicenter, chimneys were knocked down, windows broken, and frame buildings 'badly shaken.' It was noted by residents in seven states and covered 100,000 square miles." Workers in downtown office towers reported feeling the buildings sway like oceangoing vessels. The quake was felt in Georgia, Indiana, Kentucky, Mississippi, North Carolina, South Carolina and Tennessee. Aftershocks occurred for another 10 days.
Guntersville, 1957. On April 23, 1957, an earthquake struck near the Tennessee River below Guntersville Dam and was felt throughout northern and central Alabama. The GSA reported it was "felt by, awakened and alarmed many. Minor damage to several chimneys; one report of cement steps cracked in two; and several small cracks in walls. Table-top items tumbled to the floor."
Huntsville, 1959. An earthquake that struck Huntsville on August 12, 1959, damaged chimneys in Hazel Green and Meridianville and also "shook violently the buildings at New Sharon, knocking canned goods from shelves and sending frightened residents fleeing from their homes; and cracked plaster and knocked groceries from shelves at Huntsville," according to the GSA.
Palmerdale, 1975. A 4.4 magnitude earthquake struck August 29, 1975, near Palmerdale, cracking a ceiling and displacing furniture in a few homes in Palmerdale and Watson.
Littleville, 1989. On August 20, 1989, a 3.9 magnitude quake struck between Littleville and Russellville in Colbert County. According to the GSA, a basement wall collapsed in one home, but the only other damages were cracked windows and plaster. Tremors were felt in Lauderdale, Lawrence and Morgan counties in Alabama and parts of Tennessee.
Brewton, 1997. A 4.9 magnitude quake struck near Brewton October 24, 1997. It was also felt in Canoe, Lambeth, Atmore, Flomaton, Frisco City, Huxford, Perdido, Robinsonville, Butler, Demopolis, Goodway, Mobile and Uriah, as well as parts of Florida and Mississippi.
Fort Payne, 2003. A 4.9 magnitude earthquake occurred in DeKalb County April 29, 2003, 10 miles northeast of Fort Payne. The quake, which was felt in several states, was deep enough to prevent significant damage, although some chimneys were damaged and one large sinkhole formed.
Sources: Jay Reeves, Associated Press, June 13, 2015, and Kelly Kazek, Alabama.com, June 9, 2015.
