#Earthquake near Stillmore, Georgia

There was a magnitude 3.9 earthquake between Stillmore and Metter this morning at 4:05am. Here is what it looked like on the Enki seismograph in midtown Savannah …

click to embiggen. EQ is obvious, other stuff is noise from the city like air conditioners, traffic, etc.

While it was felt across South Georgia, it’s not likely it caused any major damage, although it wouldn’t surprise me if there were a couple of damage reports. It was felt as far away as Atlanta and Jacksonville. Here’s the map, computer model damage estimate < $1 Million although I’d be surprised if it is that high.

Stillmore earthquake preliminary map

This quake is in an unusual place. The sediments are deep, and we really don’t have a great picture of what is going on down there. Usually geologists write off this kind of thing as the earth readjusting to equilibrium from various stresses and strains. It does show that earthquakes can happen anywhere, not just on known faults (the key word being “known”). This one is number five on the list of strongest earthquakes in Georgia, which makes it unusual (the stronger events tend to be in North Georgia, associated with the tail end of the Appalachian Mountains, or near Savannah, associated with the fault complex near Charleston. From the early data seems quite shallow – 0.75km from the early estimates – but I don’t think I believe that (update – more data seems to indicate the depth was at 16km). Unlike the event in Poland back in April, there doesn’t seem to be anything on the surface, although there is a small man-made lake and earthen dam nearby.

A single seismograph can only compute how far away a quake is. It takes at least three stations to “triangulate” the quake location. The green band circle shows the minimum distance from our seismograph, the red the maximum. The orange “Hypocenter” marker shows the computed location based on 23 stations.

Another thing to note is the wide area over which this small quake was felt. That is because we have fairly solid rock, with wet mushy soil on top. This transmits seismic energy pretty well, unlike the highly fractured (from all the earthquakes!) rocks out west. A 3.9 near LA wouldn’t be felt nearly as far as one here is. If you’re interested in Savannah/SC Low Country Earthquakes, I did a blog post on it last fall (link). This morning’s event (probably) isn’t connected to the Charleston fault system.

We learn more after every earthquake, especially unusual ones. Will be interesting to see what comes out of further analysis on this one. If you felt this event, please go to the USGS site and fill out the “Did You Feel It?” form.

4 thoughts on “#Earthquake near Stillmore, Georgia

    • Savannah saw quite a bit of damage from the 1886 Charleston quake, but the ones near here are small, usually less than M3.

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  1. Thanks for the article. I was aware there was a fault line in the Charleston area, but heard that since the terminus of it was near Charleston, Hilton Head and Savannah had little to worry about. Is this true? What is the likelihood of a large earthquake (magnitude 5.5 or greater) occurring in the area? Does the recent increased number of earthquakes suggest something more and bigger? Thanks.

    Michael LaSovage
    12 Marsh Winds
    Hilton Head, SC 29926

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