[pct-l] Three Sisters Wilderness

[Bighummel@aol.com (Bighummel@aol.com)]

Cool.  It looks like the deformation is centered upon the PCT trace.  I 
recall a South, Middle and North Sister.  Is "Broken Top" the former South 
Sister and this "South Sister" the former Middle Sister?

JSmith writes:
"Isn't this similar to the activity around Mammoth Lakes...or has that 
quieted 
down?"

The USGS earthquake website (http://wwwneic.cr.usgs.gov/) says of a program 
that measures the deformation in the Mammoth Lakes area with two-color laser 
distance measuring instruments (geodimeters):

"The general trend of the data is 1) a general decrease in the rate of 
extension from 1983 through most of 1989, 2) an abrupt increase in the rate 
of extension on several baselines to 5 cm/yr from late 1989 through early 
1990, and 3) a decrease to 2 to 3 cm/yr extension rate that has persisted 
since mid-1990."

3 to 5 cm/yr may not seem like a lot, however, consider that this is the 
approximate average rate of slip on one of the most active faults in the 
world, the San Andreas Fault.  This movement is mostly within the Long Valley 
caldera (read mouth of a previous eruption) that is only about 30 km by 20 km 
in areal extent.

Greg

"Salvitur Ambulando"
(walking solves all things) (as in; away from an eruption, quickly!)
St. Augustine


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