Two earthquakes hit central Alabama in early November, so should we expect more?

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Montgomery, Alabama (WSFA) – Two earthquakes shook parts of central Alabama last weekend. Both are rated at 2.4 on the Richter scale, which is considered minor.

One hit northwest of downtown Clanton, and the other hit northwest of Utahn in rural Green County. Neither of them felt either, but they definitely scored.

Two earthquakes measuring 2.4 on the Richter scale hit central Alabama in early November this year (WSFA 12 News)

With it happening on consecutive days, does that mean we should expect more in the near future? Is this normal here in Alabama?

While it’s not necessarily rare for earthquakes—especially small ones—to occur in our state, it is a little unusual to have two strikes on consecutive days. Back in the late 1800s, Alabama recorded 399 earthquakes. That’s good at only three per year.

This is just the average number. You can have years with less, you can have years with more and you can have years with more than three earthquakes across the state.

For example, we only have two so far in 2021, but we saw eight in 2020 and 17 again in 2019. Each year is different on its own. There is simply no pattern of earthquake activity in Alabama and the Deep South.

We see about 3 earthquakes per year in Alabama. (WSFA 12 News)

The two who hit Central Alabama last weekend were on the weaker end of the spectrum, but that’s not always the case. Alabama was affected by earthquakes of magnitude 5.2, 4.9 and 4.6. Those incidents occurred in Arundale, Escambia County, and Fort Payne, respectively.

Once you get close to 3.5 and above on the Richter scale, people are more likely to feel an earthquake. There can be instances of damage when approaching 4.5 and above. This is especially true near the epicenter.

The reason behind the earthquake activity in Alabama is the presence and impact of two different seismic zones. The Southern Appalachian Seismic Zone causes earthquakes across the northern half of the state, while the Bahamas Seismic Zone directly causes earthquakes in southwest Alabama.

Even with nearly 400 earthquakes since the late 19th century, there are areas across the southeast with much higher seismic intensity. This includes northern Georgia, eastern Tennessee, South Carolina, and the New Madrid seismic zone along the Mississippi River.

Seismic activity is highest in North Alabama and Southwest Alabama (WSFA 12 News)

Each of these sites sees much more earthquakes than us in Alabama because of where they are located in relation to seismic zones.

These are also the locations where the “biggest” earthquakes strike; Those with intensities of 5, 6, 7 and 8. They are those types of earthquakes that can cause significant and noticeable damage and cause a much larger area to shake.

Do we deserve the “big” in the New Madrid region? And what happens in Alabama if that happens?

“The historical record and estimated probabilities of earthquakes in the New Madrid Seismic Zone (NMSZ) indicate that we must be prepared and plan for a large-scale NMSZ event,” says Sandy Ebersol of the Alabama Geological Survey.

Determining exactly when we will see a major earthquake in that region is impossible, but the chances of it occurring in the next century are very high. I asked Ebersole what the repercussions of such an event would be for Alabama…

“North to central Alabama will experience shaking from a strong (magnitude 6.0 or greater) NMSZ earthquake, with minor damage likely in northern Alabama from a 7.0+ NMSZ event.”

Copyright 2021 WSFA 12 News. All rights reserved.

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