Fast chatter on Rainier an hour ago

January 18, 2012

by John Vidale

 The chattering on Rainier showed a new pattern for a few minutes this morning, a burst of noise, then rapid pops.  The pops started out rapid, then became less frequent until they blended into the background cacophony after a few minutes.

This is 10 minutes of spectrogram (click on figure for bigger version).  The pops start out less than a few seconds apart, then spread to about 30 seconds apart by the right side of the plot.

Unfortunately, the two other stations atop Mount Rainier were feeling under the weather, and so cannot help us figure out whether the unusual signal is local to station RCS or more widespread.

Likely, something slumped on the side of the mountain, abruptly setting a glacier into motion, and the glacier skidded to a stop gradually.  Or something else happened.  Thanks to eagle-eyed seismogram-watcher Tara for pointing this out to Kate, and Kate to pointing it out to me.

[Added next day]  Seth Moran at CVO dug up another example from a year ago, clearly a small set of pops, this time near the station STAR.  Also a 10-minute record, again click for a bigger version.

[added 1/21]

and another starting at 9 UTC on 1/21 (this morning).  I'm not sure whether these are uncommonly common this week, or if we know what to look for now.  Note that while this signal is on the same station as the first one last week, it has a different pattern of vertical peaks and gaps for each pop, probably indicating activity in a different place than last week.