On the case
Rattling along a dirt road in his Silverado pickup, United States Geological Survey paleoseismologist Brian Sherrod describes features of the Wenas Valley that together tell a bigger story. He wants to know whether a scarp – a linear ridge that often indicates sudden shifts in the earth, often, but not always, from earthquakes – indicates an active fault, as he suspects. At first appearing a blur of scrub grass and shrubs, as Sherrod points out exposed basalt and deformations and slight differences in color, the scarp comes into view like one of those 3D images in a Magic Eye poster. The feature's not new to geologists, but Sherrod believes that if he can dig a trench into it he'll find more evidence of an active fault and take a step closer to describing a tectonic region far more seismically active and interconnected than once thought.
In a sense, Sherrod, a member of the Pacific Northwest Seismic Network, is a detective looking for clues of past tremors, and the faults responsible for them.
“I go around and try to identify where active faults are, and try to figure how active they are – in other words, how often earthquakes occur on these faults and how big these earthquakes are," Sherrod said.
Everything – fossils, layers of sediment, the exacting detail of data from airborne lidar mapping and magnetometers and, of course, lots of digging in the dirt – helps Sherrod solve the case. Clues might include different types of rocks on each side of a scarp or depositions known as colluvium that form when soil that should be on an upper layer shows up further below, suggesting that an earthquake rearranged the layers.
“The more we work over there, the more we're trying to fit this into a larger tectonic framework," Sherrod said of his scrutiny of the Yakima Fold and Thrust Belt.
In just the last three years alone Sherrod and his colleagues have found evidence for what are likely three newly-recognized active faults around Yakima, and even more elsewhere in the state.
“I haven't tallied it up, but I'm pretty close to finding a new active fault every year here in Washington," Sherrod says. He believes he'd find more if only given the resources to go look for them. “It takes money, it takes time, it takes people.”
One retired geologist deeply familiar with the Yakima Fold and Thrust Belt is intrigued by the study.
“We may have structures here that are actually more active than what we thought in the past, "said Steve Reidel, who was a Hanford geologist for 30 years and now teaches at Washington State University, Tri-Cities.
The author of “Big Black Boring Rock," a book about Northwestern geology, Reidel said fault records are difficult to find because scarps are rare, thanks to a different sort of cataclysm: The Missoula Floods. “Only" about 15,000 years ago, the bursting of an ice dam on a glacial lake released huge volumes of water, then over the next 2,500 years, did so about 40 times more. The floods were so forceful that they buried scarps and washed out features that might have been the best evidence of faults.
Reidel says that's why it's so crucial that geologists be given the resources to trench suspect faults – even most young faults would still be older than the Missoula Floods – so they can dig beneath the surface, beyond where key evidence may have been washed away.
“The problem is how do you get funding to do it?" Reidel asked. “We did it on weekends and evenings. As a couple of my friends said, our wives funded our research.”
Now, Reidel says, data collection that was always low key until Sherrod, Blakely, and others tarted exploring links across the Cascades, is changing the minds of people like himself.
“The way I look at it, we're just at the cusp of that knowledge base now," he says. “My attitude and ideas of what's going on over here are changing based very much on what they did, but we don't know what it all means and we don't know how significant the young faulting, because we've never really had a chance to trench some of the features.”
Even if previously unknown faults are found, that won't mean a huge earthquake is coming tomorrow, but it also won't mean there's no chance of a temblor. What it will mean is better tools with which to evaluate safety of places like Hanford and the Columbia Generating Station. It also doesn't mean Reidel will leave town any time soon.
“The west coast is particularly dangerous [for earthquakes], but the best way to look at it is the probability of a big earthquake is the same every day and it's pretty small," Reidel says. “Some day you're going to have that earthquake. You don't know when, but you're going to have it, but it's still a small risk every day.”
Questions about the Columbia Generating Station's safety didn't start with Fukushima. Last fall the Associated Press reported that the industry-funded Institute of Nuclear Power Operations said the plant was one of two in the nation most in need of improvement. In 2009, the plant had five unplanned shutdowns – known as “scrams"– KING 5 News reported this April.
Energy Northwest officials refused requests for interviews for this story, but three days after the Tohoku quake, company officials assured a jittery public that the Columbia Generating Station was well prepared for the unlikely event of natural disaster, thanks to redundant backup power systems, a safe distance from the Columbia River in case the upriver Grand Coulee Dam bursts, and engineering that would help the plant weather ground shaking exceeding what would come from the largest earthquake expected in their region
Two weeks later Energy Northwest CEO Mark Reddemann penned a widely-circulated op-ed further detailing the plant's preparations and meant to counter public apprehensions about nuclear power.
“In the past weeks, too much misinformation about nuclear energy has played on people's fears," Reddemann wrote. “The anti-nuclear lobby has seen an opportunity and they are exploiting it."
In the op-ed, Reddemann said this wasn't the time to debate the merits of developing additional nuclear power resources in the U.S. Rather, he wrote, the nuclear industry will thoroughly study in minute-by-minute detail to incorporate lessons learned once the situation at Fukushima stabilizes and can be studied.
“What you should know - and may know already - is that your friends and neighbors who work at Columbia Generating Station have an unwavering dedication to safety," Reddemann wrote.
On March 10, only a day before the Tohoku quake, Energy Northwest received the latest in a series of letters from the NRC questioning the sufficiency of calculations the company used to inform its cost-benefit analysis of earthquake impact mitigations. A July 1 2010 letter, meanwhile, reveals NRC's concern that Energy Northwest used old seismic hazard analyses to measure ground-shaking, despite more recent studies of earthquake hazards, like ones done by the USGS or the Pacific Northwest National Laboratory for projects related to the cleanup effort at nearby Hanford.
The NRC's Dricks said these letters only seek to clarify technical details and don't cast doubt on plant safety.
“There is no reason for people living near the plant to fear for their safety," Nuclear Regulatory Commission spokesman Victor Dricks said in an email.
Dricks later said that Energy Northwest's response to the March 10 letter, as well as some unanswered questions from the July 2010 letter, is due May 9.
Energy Northwest did respond to the seismic hazards question from that letter in a Sept. 17 response. It told the NRC that the Columbia Generating Station is farther away from seismic sources in the Yakima Folds than the Hanford facilities in question, with different soil structures underneath. Moreover, the response continued, a 2005 study at Hanford suggest that estimates of hazards were similar to what earlier studies had shown, and that data from a 2008 USGS hazard map suggests the company was actually being more conservative than necessary in predicting ground motion.
The question will now become whether the next USGS hazard map – scheduled for release in 2014 – will include updated information about hazards in the Yakima Fold and Thrust Belt. That will depend in large part on how much study the Pacific Northwest Seismic Network team is able to do on the region and on what new knowledge research like that done by Sherrod and Blakely brings to the table.
Thursday: Preparing Hanford for a major earthquake
This story was funded in part by the Spot.Us community