On Sat, 10 Jun 2000, meredith lamb wrote:

> Hi all,
> 
> The Denver Post newspaper ran a article on June 8th, 2000,
> of a injection well to dispose of brine water 14,000 feet into
> the earth.  Seems there has been some 1500 mostly very
> small associated quakes since 1991.  The recent 4.3 quake
> has brought with it changes in operation.  See:
snip

Meredith,

The interesting thing about all this was that last year there were two 3.7
earthquakes in the Paradox Valley associated with deep well injection.  In
an article published at that time (Grand Junction Daily Sentinel), a
representative for the Bureau of Reclamation said they weren't going to
get worried about the earthquakes until they went over 4.0.  Well, they
just went over 4.0.  

The project has worthy goals, the desalinization of the Dolores
(ultimately the Colorado) River.  The concern?  Once you start the process
of deep well injection, how much control do you actually have over the
magnitude of the earthquakes?  We have seen a steady, yet slow increase in
magnitudes.  This would follow the pattern established in the deep well
injection project at the Rocky Mountain Arsenal, near Denver, in the
1960s.  While the frequency of the earthquakes at RMA somewhat matched the
frequency of pumping, the magnitude of the associated earhtquakes did
not.  The project, started in 1962, produced magnitudes 5.3 and 5.1 by
late 1967 (see Kirkham & Rogers, Colorado Geological Survey Bulletin
43).  As was the case in Denver, the tectonic stresses in the Paradox
Valley existed prior to the deep well injection project.  The control of
those stresses may now be out of the hands of the BOR.  But, perhaps not.  

From a seismology point of view, I have a seismic experiment in my own
backyard.  Can't wait to see what happens next.

Dave Wolny
Mesa State College
Grand Junction, Colorado
dwolny@.............
station MSCO



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