Pump in West Primes Earthquake
Monday, November 15, 2004 Posted: 8:34 AM EST (1334 GMT)
The McPhee Dam and Reservoir on the Dolores River
GRAND JUNCTION, Colorado (AP) -- A federal facility that pumps salty water
14,000 feet into the Earth's crust probably is associated with a magnitude
3.9 earthquake that struck the Utah-Colorado border this month, an official
said. The U.S. Bureau of Reclamation facility removes salt from the Dolores
River, then pumps 230 gallons of brine per minute into deep wells in Utah's
Paradox Valley Area. The process is intended to decrease the salt content
of the Colorado River downstream, but scientists say it also lubricates
faults. The facility has caused thousands of earthquakes in the area since
1991, but most have been too small for people to feel. The 3.9 quake,
which struck November 6, was felt in Grand Junction, some 60 miles away.
No damage was reported. "We have a seismic network set up for measuring
and recording any events associated with the injection process, and it
appears this earthquake was one probably associated with that process,"
said Andy Nichols, manager of the federal facility. "Every once in
a while there's a large event felt at the surface, and this was one of
those events."The last large earthquake occurred in May 2000 and
registered 4.3 on the Richter scale. An earthquake of magnitude 6.0 or
greater are generally destructive.
That event, combined with two significant tremors in 1999, led government
officials to reduce the amount of brine injected by a third.