Third earthquake in under two weeks shakes the region on Sunday. At magnitude 2.2, it was the strongest of the trio and again struck near Tunnel Hill.

Third earthquake in under two weeks shakes the region on Sunday. At magnitude 2.2, it was the strongest of the trio and again struck near Tunnel Hill.

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An earthquake registering a 2.2 shook parts of Tunnel Hill near Dalton around 1:30 p.m. Sunday. It was the third quake since Dec. 29 in the region and the second near Tunnel Hill. Sunday’s quake was the strongest of the three at 2.2 The Ooltewah quake was 2.1 on Dec. 30; the first Tunnel Hill quake was 1.99 on Dec. 29.

Details below about our quake zone.


 

For your “2020 Believe It or Not Bingo Card:” Twin earthquakes in our area on Tuesday and today. The U.S. Geological Survey reports two small earthquakes rattled parts of Northwest Georgia and metro Chattanooga in the past 24 hours.

  • The first as in Tunnel Hill around 8:40 a.m. Tuesday with a magnitude of 1.99. (Baby blue dot on the above map).
  • The second was in Ooltewah just northeast of Chattanooga at 1:55 a.m. Wednesday. It was a bit stronger, 2.1 magnitude. (Red dot on the above map).

What to know: Tectonic Summary

Earthquakes in the Eastern Tennessee Seismic Zone: The Eastern Tennessee seismic zone extends across Tennessee and Northwestern Georgia into northeastern Alabama. It is one of the most active earthquake areas in the Southeast. Although the zone is not known to have had a large earthquake, a few earthquakes in the zone have caused slight damage. The largest known (magnitude 4.6) occurred on April 29, 2003, near Fort Payne, Ala. Earthquakes too small to cause damage are felt about once a year. Earthquakes too small to be felt are abundant in the seismic zone, and seismographs have recorded hundreds of them in recent decades.

Earthquakes everywhere occur on faults within bedrock, usually miles deep. Most of eastern Tennessee’s bedrock originated several hundred million years ago, as the Appalachian Mountains were formed.

At well-studied plate boundaries like the San Andreas fault system in California, often scientists can determine the name of the specific fault that is responsible for an earthquake. In contrast, east of the Rocky Mountains this is rarely the case. The Eastern Tennessee seismic zone is far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea. The Eastern Tennessee seismic zone is laced with known faults but numerous smaller or deeply buried faults remain undetected. Even the known faults are poorly located at earthquake depths. Accordingly, few, if any, earthquakes in the Eastern Tennessee seismic zone can be linked to named faults. It is difficult to determine if a known fault is still active and could slip and cause an earthquake. As in most other areas east of the Rockies, the best guide to earthquake hazards in the seismic zone is the earthquakes themselves.

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