Mount Rainier popping away
January 8, 2012
by John Vidale
Something is moving on Rainier, almost certainly the glaciers, as discussed in the last blog post by Kate. Below are the last ten minutes in a spectrogram plot. It shows the recordings at four different stations, and indicates a string of tiny earthquakes (we call them icequakes, even they do shake the Earth).
Below is the more traditional seismogram plot, accesible through this link, showing the last 6 hours of unremitting activity. It shows the vertical motion at the station STAR, which is right on the side of the volcano.
For plot purists, the plot above shows activity at 22:30 UTC, which is 2:30pm here in Solstice Cafe on University Ave by UW. This 10-minute interval, with 4 or 5 bursts of motion, is the 3rd line from the bottom on the plot below. Each line plots ten minutes of activity, and the slightly different colors of blue distinguish the different 10-minute lines. From the plot above, it is apparent that there are numerous tiny vibrations in addition to the larger (though still small) bursts.
This yammering has been non-stop for several days, and can actually interfere with monitoring the seismic network, as events are frequently triggering the earthquake detection software, filling the queue to process, and fraying the nerves of our analysts.
Not to mention vexing those of us who are never really sure we understand our observations as well as we think we do.