See the Earthquake!

A seismograph located in the Dow Environmental Sciences and Engineering Building has recorded a magnitude 8.0 earthquake just off the Pacific island kingdom of Tonga.

The quake occurred shortly before noon Wednesday (Houghton time). You can see the record at the web site .

This web site is updated every 10 minutes (you may need to refresh your browser). Eventually, the earthquake record will be replaced with newer data, but it will be visible for the next 20 hours at least.

So why is there a seismograph on the ground floor of the Dow Building (and another one in the Houghton Middle School)? "Earthquakes send out seismic signals, and these, if the earthquake is large enough, are recorded around the world. Witnessing the recording of a large earthquake can be an exciting event, no matter where it occurs," says Wayne Pennington, chair of the Department of Geological and Mining Engineering and Sciences. The seismograph in the Dow Building is in a vault where it is relatively isolated from building vibrations and air currents, but you can see the seismograms it creates on the seismograph website.

This site is automatically updated every 10 minutes; you might need to refresh your browser to see the changes. If you go to the seismograph web site within 20 hours of the earthquake's occurrence, you will be able to see the seismogram it created. The seismogram from this earthquake will be over-written with new data (presumably less interesting) starting at 8 a.m. on Thursday, but the later aftershocks (coming in over a period of several hours) will be visible through most of the afternoon. The data are saved in electronic format and can be studied at any time. A seismogram of the tragic 2004 Sumatra earthquake is displayed, at a reduced amplification and shortened time scale, at .

The data is displayed in two formats. The main one consists of a series of four-hour strips, with the time compressed to fit across the screen, and the second one shows just the most-recent 30 minutes of data, in an expanded time scale, near the bottom of the screen. Because this earthquake is so large, most of the first few hours show the up-and-down oscillations of the earth (yes, here in Houghton) as a solid band because the amplitude is so large. The later hours will show the individual waves more distinctly, as they diminish in size from traveling around the world multiple times. At the time that this article is written, there were no large aftershocks recorded, Pennington said, but you might expect to see one or two by Thursday or Friday. The largest ones are typically about one-tenth the amplitude of the mainshock.

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Department of Geological & Mining Engineering & Sciences
Michigan Technological University
1400 Townsend Drive - Houghton, MI 49931-1295
(906) 487-2531