Early the morning of Tuesday, February 21, 2012, there was a minor earthquake reported a few miles outside of Sikeston, Missouri. It was initially reported as a 4.0 but was later downgraded to a magnitude of 3.9. This is the largest earthquake in the area since a similar 3.9 reported in Missouri last June, but this occurred much more explicitly along the New Madrid fault line. From the USGS:
Going back to 1990 in the ANSS catalog I found that quakes of around this magnitude or greater are recorded in this area every year or two on average. I tried to graph the top 50 quakes since 1990 in the range of latitude 34N to 38N, longitude 94W to 88W, with a comparable map slice:
The black circle under the 37N line is the February 2012 quake – same as the biggest yellow square in the map slice below. The thick-looking group of circles under 35.5N are the biggest quakes from the Arkansas activity of the last two years that I suspect to be related to fracking. The groups of circles nearer the black circle are the New Madrid area, and these quakes are spread out over the last twenty years of the data I analyzed. So this recent quake does not appear to be out of the ordinary regarding size, location, and timing.
An update of my Midwest quake activity graph shows a continuing overall lull in activity from both the western “Arkansas” half and the eastern “New Madrid” half of my slice. At least for now, it looks like the fracking activity is subsiding and has not been bothering the New Madrid fault line, either.
My name is Joshua Hedlund. Welcome to the Joshua Science blog. I keep these posts separate from my main blog because they involve topics would be considered "boring" to most of my family, friends, and general readers. I'm a data junkie and statistics nerd who also happens to have a insatiable desire to understand the world, so sometimes when I come across publicly available data about earthquakes, ice levels, tornadoes, and more, I like to analyze that data and present my findings here.