Water 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.