Monday, September 25, 2006

Another earthquake in Cheraw ...

Matt B left a msg on my phone at about 1:45 am EDT, just after another noticeable earthquake in the Pee Dee. (The last one was last Friday). Here's the data on this one from USGS: 3.7 magnitude, shallow focus (about 3 miles depth). Here's the epicenter map, clearly they're on fault lines close by (or even on the same one). Here's the past six months of seismic activity in the Central and Soutehrn US: notice the clusters: the Appalachians, the Adirondacks (rebound seismicity, as the earth slowly rebounds after being compressed for all that time under ice), the Mississippi Valley. The Carolinas are moderately active, but there's been no significant recent activity. [I think for the USGS, a quake becomes "minor" if it's mag. 3.0 or greater on the Richter. Recall too that the Richter scale is exponential, so a mag. 5.0 releases a heck of a whole lot more energy than a msg. 3.0, for instance.]

Don't ask me what this means -- I'm not a seismologist. Earthquakes are practically impossible to predict, as in, "there will be one of this magnitude at this time at this location." I don't know anything about the more recent seismic activity of the Carolinas ... obviously devastating earthquakes can happen, as the Charleston quake of 1886 shows. The region is moderately active with respect to seismicity, so a few minor tremors here and there are hardly unexpected. It's good to keep a perspective based on geologic time on these things! :)

[Both earthquakes made The State. However, clicking on each headline opens a blank page in both browsers that I use. Or rather, a page loads with everything on there, including the headline, but no story! Weird.]

More info on SC seismicity at the South Carolina Seismic Network at USC.
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