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New Madrid earthquakes over time


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New Madrid earthquakes over time

Here is an animated view of the New Madrid Seismic Zone with the earthquakes played back over time. This makes it easy to see clusters of quakes happening in quick succession. The quake data is from the Center for Earthquake Research and Information at the University of Memphis, and it spans the time period from June, 1974 through July, 2011 in 3 minutes and 47 seconds. That’s almost too much time compression, but it works.

As for the production of the video, there is a lot of data and a limited viewer attention span. If each frame was one day, e.g., and the frames assembled into an animation, the individual earthquakes would flit by way to fast to register. The solution, as you see, was to show each quake for several frames spanning a few seconds, fading it as it ages. That makes each quake noticeable and increases the ease with which clusters of earthquakes can be discerned from the animation.

The year clock widget shown in the lower left is what I came up with to show the time scale. And, yes, the fading swath of red directly corresponds to the fading earthquake points. If you’re able to correlate the shade of a quake to the red on the clock, you can determine exactly when it happened. “If”. That’s not really practical, but nonetheless, you can see some value in presenting the timeframe this way. Well, I can anyway.

Data for the state lines and cities were read from a text file, already projected to UTM zone 15 North. This is getting a bit too far east for that zone, but the left side of the map is too far west for Zone 16 North. Such is life lived on the edge. The quake data likewise was preprojected to 15N. This was done with the Proj4 utility.

Anyway, each frame was rendered by a Perl script, using the GD package, by drawing the state lines, the cities & names, the side bars and clock, and the relevant quakes. The quake data was read from a file with all quakes for a given day grouped into one list. The last 30 days of quakes is drawn on each frame, the shade and opacity of the dot corresponding to its age, and the diameter to its magnitude.

Most quakes here, by the way, were too small to be felt. There are a few moderate shakers represented, but nothing serious.

Titles and credit frames were rendered separately, and the whole rendered into an animation with ffmpeg. A soundtrack was found that more-or-less fit the mood and the length of the animation, and the result is in front of you. That’s not my first choice of soundtrack for this video, but Elvis Presley’s “All Shook Up” was not available. The drum solo works okay, but it would have been nicer if some of the big beats actually synched up with some of the quake action.

The Perl script used to render the frames, but not the data, is on the code page. I didn’t write this for school or for work, so it’s not too well annotated. And since I actually did most of this work 2 months ago, I’m not prepared to go back and reanalyze it to add any more commentary than it already has.

Note the varying licenses on the audio and the video. I’m not too proprietary and offer the video under the Creative Commons CC-BY-3.0 license. But the audio portion is under the more restrictive CC-BY-NC-3.0 license. The audio is Oddly We’re Even by Bill Ray.



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