Imaging Magma Under St. Helens

The iMUSH "active" experiment is over.  2,500 sensors are yet to be recovered from the field but the shooting is done.  All shots went off successfully though there was a bit of nervousness due to some lightning in the area.  It was never close enough to effect operations but made for a nice display.  It appears all shots were well recorded on the PNSN stations and certainly should have been on most of the iMUSH portable sensors (though it will be days to weeks before the data are all recovered, checked, organized and ready for the real scientific analysis). Today the volunteers are headed back to the field to again drive and hike the region around the mountain to recover all of the sensors.  Crews at the logistics centers south and west of the volcano will down-load data as the recovery teams arrive back and preparations will be made to ship all of the equipment back to the PASSCAL instrument center next week.

Professor Alan Levander, who is the lead scientist for this experiment has expressed great satisfaction with the apparent success.  In particular he "would like to thank Ryan Cole and his colleagues at the US Forest Service, and Ellie Lathrop and her colleagues at Weyerhaeuser Corporation, as well the Department of Natural Resources, WashDOT, various counties in Washington and Oregon, and numerous private land owners around Mt St Helens.  He also expresses his thanks for the army of volunteers who braved the rain storms of last week and the heat of this week to deploy and recover the huge number of instruments".

Here is a webicorder (seismogram) for station TDL, located north of Spirit Lake for last night. The shot signals are marked with red arrows, a small earthquake (Mag=2.5) east of Seattle is marked in black and the large signals from the automatic station calibration system are near the top.  Other signals on the records are mostly from vibrations generated near this station such as deer moving around.  (BTW the difference in colors for the lines on these sorts of plots is only to aid your eye in distinguishing one line from another.)

Here is a map of the shot locations as determined by the Pacific Northwest Seismic Network (PNSN).  Actually thee of the "shots" located on this map are actually quarry explosions done independent of the iMUSH experiment by commercial operators in the area.  Such events are typical of any 10 day period.

 Here is a comparative map of the same region for the period Jul. 20 - Aug 1, 2014 showing the earthquake epicenters as determined by the PNSN.  Earthquake depth is color coded with red < 1 km deep and grading to blue > 10 km deep. Most of these earthquakes are smaller than magnitude 1.  Natural seismicity in the Mount St. Helens area may have had a slight increase over the past month (starting considerably before the shooting), though much of the apparent increase in number of events is due to new and extra efforts by PNSN staff to detect every possible event no matter how small.  See PNSN blog on this topic.