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EARTHQUAKES
IN ALABAMA
Earthquakes are fairly common in the eastern half of the United States.
Four zones of frequent earthquake activity affecting Alabama (right) are the New Madrid
Seismic Zone, the Southern Appalachian Seismic Zone, the South Carolina
Seismic Zone, and the Bahamas Fracture Seismic Zone.
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.
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INTERACTIVE
EARTHQUAKE MAP OF AL
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Earthquakes
are not uncommon in Alabama. The interactive map to the
left shows epicenters of historical Alabama earthquakes from 1886 to 2011
and surface and basement faults. To read more information on individual
earthquakes or faults, click the feature on the map.
Not
all web browsers or connection speeds support the below interactive map. If
you do not see the map to the left, click here.
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GIS shapefiles and metadata of
earthquake epicenters and surface faults in Alabama (as seen on the map to the left)
are available on our Geospatial Hazards Data page.
For a catalog of Alabama
earthquakes (as of October 2012), click
here to download the Excel file.
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HISTORICAL
EARTHQUAKES IN ALABAMA
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Building
damage caused by the Fort Payne 2003 earthquake included broken windows,
minor cracks in masonry (below), and chimneys that collapsed or broke at
the top (above). Some schools in the area were closed
as a precaution although no structural damage was recorded.
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Fort Payne
Earthquake, 2003
On Tuesday morning,
April 29, 2003, a 4.9 magnitude earthquake occurred in DeKalb
County, Alabama, 10 miles
northeast of Fort
Payne. The quake was felt in multiple southeastern states (below). The
earthquake was deep enough to suppress significant damage in Fort Payne, the closest city, although
the event did damage weaker masonry.
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The Fort
Payne magnitude 4.9 quake caused the development of minor landslides such as
the one above, sinkholes like the one below and, muddied the underground
water supply for the town of Valley
Head, causing the pumps to shut down.
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Escambia County
Earthquake, 1997
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The second largest quake recorded by
seismographs in Alabama occurred on
October 24, 1997, in Escambia
County (left) and was
a 4.9 magnitude event. Effects from the shaking were seen
as far away as Lawrence
County where a berm around a pond failed, spilling water and fish
across a road. Large cracks also developed in sand along a creek (right).
Shaking from the quake was felt into Mississippi.
The southwestern part of Alabama has had
minimal seismic activity recorded by seismographs. However, the largest
historical earthquake known for this area occurred in 1781 in the Pensacola area. The
quake is recorded to have caused structural damage
(read more below).
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Irondale Earthquake, 1916
The largest known earthquake in Alabama
happened October 1916 in northern Shelby County
(below). Intensity was estimated to be a VII on
the Modified Mercalli Scale, indicating a moderate earthquake. Geologists
estimate the magnitude was about 5.1.
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Pensacola Area Earthquake,
1781
According to USGS earthquake records, a large
magnitude (6-7) earthquake occurred in the Pensacola area in May of 1781. Although
there were no fatalities recorded in association
with the shaking, damage reported included ammunition racks torn from
barrack walls and a leveled house in the vicinity.
This earthquake, and the Escambia County
earthquake in 1997 were both associated with basement faults that run from
the Florida panhandle through southwestern
Alabama and into southeastern Mississippi. These faults are
believed to be associated with the Bahamas Fracture Seismic Zone, a
crustal zone of weakness associated with the formation of the Gulf of Mexico.
More Historical Alabama Quakes
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Additional
information on earthquakes in Alabama
and the role of Alabama Emergency Management Agency (AEMA) can be found on the AEMA website in the brochure
Earthquake Awareness for Alabama Residents. Click the brochure to the
right to go to the website, or click here to download the pdf.
The
USGS also has additional information on earthquakes in Alabama and our neighboring states. Click
here to read more.
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SEISMIC STATIONS
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The U.S. Geological Survey (USGS) installed
a broadband seismic station in Bibb
County in June
2001. The station (photos below) was funded through a
grant from the AEMA and arranged by an agreement between AEMA, the USGS,
and the Geological Survey of Alabama (GSA) and is part of the
Advanced National Seismic System (ANSS) coordinated by the USGS. The site
for the station is located near the middle of the state in Bibb County in the southernmost
exposure of hard Paleozoic rocks.
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The station is able to monitor even
small earthquakes that generally go unnoticed but may be precursors of
future larger quakes. Information from the sensors goes to an onsite computer (left),
which then relays the information by satellite (far right) to USGS
headquarters in Golden, Colorado.
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The stations sensors are placed
4 feet underground and can sense everything from vehicles passing by to
earthquakes on the other side of the earth. The two sensors at the
station are buried in large water-tight
containers. A small shed houses the accompanying electronics (above
middle and right).
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Seismic stations in and around Alabama
(locations from International
Registry of Seismograph Stations).
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ALABAMA SEISMIC DATA REAL TIME !
Curious to see what seismic
stations in Alabama
are recording today? Copy and paste one of the urls
listed below to go to its corresponding helicorder
(a compiled record of vibrations recorded by the station).
BRAL, Brewton, AL (USNSN,
Broadband) S AL
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LRAL, Lakeview Retreat, AL
(USNSN, Broadband) Central AL
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FPAL, Ft
Payne, AL (CERI, Broadband) NE AL
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PWLA, Pickwick Lake, AL (CERI,
Shortperiod) NW AL
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PLAL, Pickwick Lake
(SLU, Broadband) NW AL
HSV,
Huntsville (Public Seismic Network,
Broadband) N AL
(currently not shown on map)
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ADDITIONAL ALABAMA
EARTHQUAKE INFORMATION
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Earthquake Hazards Map
To produce your own Earthquake Hazards Map such as the
one to the right, click
here to go to the USGS Custom Hazards Mapping tool. The colors on the map refer to an
estimate of the probability of exceeding a certain level of ground shaking
in percent g (gravitational force) in 50 years. This is dependent on
magnitudes and locations of likely earthquakes, occurrence frequency, and
properties of the rocks and sediments of the area.
For additional information on how these maps are
generated, click
here to go to the USGS webpage on Earthquake Hazards
101.
For the U.S. National Seismic Hazards Maps 2008
edition and 2010 revisions, click
here.
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Seismic Engineering
For seismic design information for engineers, please refer to the USGS
webpage Seismic
Design Maps and Tools for Engineers.
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Earthquake Probability Mapping
For earthquake probability mapping of an area of
interest in Alabama,
click here to refer to
the USGS 2009 Earthquake Probability Mapping page. The page requires input
of a latitude/longitude of interest (such as for that of a city) and an
area map (such as the one to the right) is produced showing estimated
earthquake probabilities computed from the source model of the 2008
USGS-National Seismic Hazard Mapping Project (NSHMP) update.
For documentation on the USGS online program that produces the maps such as the one to the
right, click
here.
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Alabama
Earthquake Notification
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Additional Questions?
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If
you would like to receive a text message or email when an earthquake occurs
in Alabama,
click here to sign up
through the USGS automated Earthquake
Notification System.
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If you are looking for additional
Alabama-specific earthquake information not found on these pages, please
contact Sandy Ebersole, sebersole@gsa.state.al.us,
205-247-3613. For earthquake information specific to other states, please
refer to that states
geological survey or the USGS.
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