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.
With 2011 behind us, it’s time to take a look at the year in earthquakes. Here are the 10 most powerful earthquakes that were measured in 2011 by magnitude, according to the data pulled from the ANSS Catalog.
9.1 magnitude. March 11, 2011. (38.297, 142.373). This was the devastating earthquake that occurred off the coast of Japan. Many other sources list the earthquake as a 9.0, including the Wikipedia article which contains heavy details about the destructive earthquake and the tsunami that followed. This quake was more powerful than the 8.8 which struck Chile the previous year on February 27, 2010, but less powerful than the 2004 Indian Ocean quake, which was considered a 9.1-9.3. Wikipedia considers Japan’s quake the fifth-most powerful ever recorded, while InfoPlease lists it at #4.
7.9 magnitude. March 11, 2011. (36.281, 141.111). This was a huge aftershock that occurred about 29 minutes after the 9-magnitude quake. For comparison’s sake, the largest aftershock recorded from Chile’s 8.8 quake was a 7.4 about 90 minutes later. The Indian Ocean quake registered a 7.2 approximately three hours later.
It’s been a couple months since I last looked at the earthquake activity around the New Madrid fault line, and it’s time for an update from the ANSS catalog data.
I’ve spent a lot of time analyzing the publicly available earthquake data for the area around the New Madrid fault. This year we saw a huge jump in recorded earthquakes for Arkansas, but my analyses have shown they have almost all been recorded within an extremely small area that seems to be related to fracking, and they have almost all had a magnitude smaller than 3.0 with the occasional quake barely registering above all.
When we looked at the northern polar ice cap last month, it was in danger of setting a new record low. Fortunately, that did not happen. The melting slowed, and this year’s summer minimum was “only” the second-worst in our relatively short record. Here’s the current graph from IJISI, with this year in red:
And here is my updated graph comparing this year’s run with previous years:
Right now 2011 is among the year’s highest spread compared to the record-low year of 2007, mainly because right around this time four years ago the polar ice cap dropped into its record-low extent. But it’s not just 2007, this year’s average spread compared to the last four years is among it’s best so far this year as well. As always, though, caution is in order. After appearing to hit an earlier minimum this year, the ice cap recovered quickly to 2008 levels (dark green line in the IJIS graph), and is has since mostly stalled. The future is ever uncertain.
Update: New Madrid Fault Activity – November 2011 Update
Beginning in October 2010 it looked like New Madrid fault activity was increasing significantly (it turned out be completely attributable to a random location in Arkansas, with the best theory having to do with fracking or man-made drilling). The actual New Madrid location was showing no such increase when I looked at the data in January, or again when I looked at the data in March. It’s been a few months since then, and I haven’t seen any more headlines about the local earthquakes, so I thought it was time to browse the ANSS catalog once more.
It looks like we’ve returned to normal activity in the Arkansas location (which I’ve defined as latitude from 34 to 38 and longitude from -94 to -91). Most of the summer has seen between 0 and 12 quakes per week. There has been a slight shift: most of the previous upticks on the graph occurred in an area very near the point [35.2, -91.3], while the most recent tiny uptick in July shows a handful of activity very near the point [35.3, -92.6]. Assuming that this activity is caused by fracking, perhaps they have moved. If so, they are causing much less disturbance than they were a few months ago.
Meanwhile, there’s been a continuing lull in the New Madrid location (which I’ve defined as latitude from 34 to 38 and longitude from -91 to -88), where we saw between 0 and 5 quakes per week in the last few months. It certainly doesn’t appear that the June St. Louis earthquake has disturbed the old New Madrid, nor the recent oddball quakes in Colorado or Virginia.
And for fun, I’ve got an updated comparison with the San Andreas fault area. The first graph shows the raw number of quakes recorded in the areas I defined above compared with my arbitrary San Andreas bounds of latitude between 33 and 42 and longitude between -125 and -115. Since that area is much larger than the other two areas, the second graph shows a normalized number that compares equivalent ratios per area.
Feel free to dispute my methodology. My bounds are arbitrary but I feel they present accurate information. The San Andreas fault still records many more quakes per square mile over a much larger area than the New Madrid does. Several months ago, the Arkansas location almost averaged as many quakes in its area as the entire San Andreas fault does all the time over its entire area, and that has since dropped back to normal, with the exception of the brief Arkansas uptick in a slightly shifted location.