Two Earthquakes Strike Alabama Northwest of Birmingham

The two earthquakes struck at about the same place hours apart at the orange dot inside the colored concentric circles on this map. Image: USGS — The two earthquakes struck at about the same place minutes apart at the orange dot inside the colored concentric circles on this map. Image: USGS

According to USGS, Alabama was rattled by two earthquakes practically in the same location last night, north and west of Birmingham. The first earthquake struck near Addison at 9:17 pm from a depth of 16.2 km; it was rated a magnitude 2.4 event. The second earthquake struck about 40 minutes later at 9:59 pm about 4,000 feet north and east of the first from a depth of 14.8 km; it was rated a slightly weaker magnitude 2.3 event. No damage or injuries were reported from either quake.

Earthquakes with a magnitude of 2.0 or less are rarely felt or heard by people, according to USGS, but once they exceed 2.0 more and more people can feel them. While damage is possible with magnitude 3.0 events or greater, significant damage and casualties usually don’t occur until the magnitude of a seismic event rises to a 5.5 or greater rated event.

Earthquakes are not uncommon in Alabama. This map shows epicenters of historical Alabama earthquakes since 1886 and surface and basement faults. Image: Geological Survey of Alabama

According to the Geological Survey of Alabama (GSA), earthquakes aren’t completely rare in the state. According to GSA, “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.

The strongest earthquake to ever hit the state was a magnitude 5.1 event in 1916 in northern Shelby County.

The second and third strongest earthquakes were each rated as a magnitude 4.9 event. One struck in DeKalb County, 10 miles northeast of Fort Payne, on April 29, 2003. The earthquake was widely felt across the northern half of Alabama and Georgia, much of Tennessee, and even portions of Kentucky, North and South Carolina, and Mississippi. The other struck in Escambia County on October 24, 1997; that earthquake was responsible for a berm around a lake to fail, spilling water and fish across a road. Large cracks also developed in sand along a creek not far from the epicenter. Both 4.9 magnitude events did some damage, mainly to weaker masonry found in the northern part of the state.