New Quake Concerns At Nuclear Dump Site

When geologist Brian Wernicke set out to study shifting faults in eastern California, he needed to find someplace relatively nearby that was stable - a stationary spot against which to measure movement in the two California fault zones.

He picked Nevada's Yucca Mountain. And that choice may have consequences that echo all the way to Congress.

Dr. Wernicke and his colleagues have discovered that the area is anything but stable. Their measurements indicate that Yucca Mountain - the proposed site for a federally run nuclear-waste dump - is at least 10 times more likely to experience an earthquake or volcanic eruption than previously thought.

The findings, appearing in today's edition of the journal Science, come at a time of intense wrangling in Washington over high-level radioactive waste from the nation's 109 commercial nuclear plants. Federal courts have ruled that the US Department of Energy must take the waste, but the DOE counters that it can't take any before the president approves a permanent site.

To speed the hand-over of waste, both houses of Congress have passed bills that would designate Yucca Mountain as a temporary storage site - despite President Clinton's threat to veto any such measure. The study could become the latest rallying point for opposition to Yucca Mountain as a temporary any sort of permanent nuclear-waste facility.

Financed with grants from the National Science Foundation and the US Nuclear Regulatory Commission, Wernicke and his colleagues set up 10 Global Positioning Satellite (GPS) receivers among the two California fault zones and five receivers in a line that cut across Yucca Mountain.

Previous studies indicated the crust around Yucca Mountain was stable: "When you look at the geological record, it didn't indicate much activity," says James Davis, a geodesist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

But the team, which included researchers from the California Institute of Technology in Pasadena, Calif., and the Center for Astrophysics, began to see the first hints of significant motion at Yucca Mountain in 1995. The rates of movement in the earth's crust around the site "were surprising; we didn't really expect to see them," says Wernicke, a geology professor at Caltech.

Based on GPS information from the satellites alone, the crust near the mountain is heading west-northwest at nearly 2 millimeters a year - roughly three to four times the average for the basin and range region in which Yucca Mountain sits.

When the team, which has been working since 1991, incorporated data from other surveys dating back to 1983, the rate still remained a relatively high 1 millimeter a year. "This indicates a greater hazard for seismic activity than might have been expected based on the geological record," Dr. Davis says. "These are the first data of present-day deformation" at Yucca Mountain.

Wernicke acknowledges that the results are "a rough cut." Answers to questions about the sources of the strain - and where and how the strain is most likely to be released - would require additional measurements, he says.

Planned seismic- and volcanic-hazard assessments for the DOE's Yucca Mountain project have already been completed, says Richard Quittmeyer, a seismologist involved with the Yucca Mountain project-management team. Yet the study could reopen the discussion about seismic risks at the site. "As new information becomes available," he says, "we'll have to consider its impact on our assessments."