Monday, April 18, 2011

The Earthquake That Wouldn't Stay Put

It all started with the Hydro-Thermal program, a very big 1950s idea that ultimately crashed very hard in the 1980s with the largest municipal bond failure in the history of the country.  The big idea was that the Northwest electrical need was growing quickly and the Columbia River was all dammed up and our electrical growth would soon outpace our ability to make enough of it.  So, to save the aluminum industry, to serve customers whose demand, according to the forecasters, would triple in the 20 years between 1970 and 1990, the engineers driving the power system proposed building more than 20 nuclear and coal plants along with 20 or so new dams. 
We'll return to Hydro-Thermal one day, but this story is about an unintended consequence of it – the demand for seismic knowledge in the Northwest that went through the roof as project sponsors sought to license new facilities throughout the region.   It was a great season to be an earthquake guy.  Better yet, we are safer today because of the sophisticated knowledge of our seismic character kicked off by this gold rush for new electrons.
Monte Dolack Poster used in campaign
to stop Skagit nuclear plants.
Building a nuclear power plant requires an analysis of the biggest earthquake in the past that might affect the structural capabilities of a plant in the future.  With potential sites scattered all around the region, one engineering company’s placement of the epicenter of an event became an increased risk to other engineering companies and their plant-building clients.  That’s what happened to the earthquake of 1872, likely the biggest earthquake in the interior of the state of Washington.
Our story starts with Puget Sound Power and Light, today's Puget Sound Energy, working against considerable local opposition to build two nuclear plants near Burlington in Skagit County. 
Conventional wisdom, and a Canadian seismologist named W. G. Milne, had the epicenter of the 1872 quake about a hundred miles east of Vancouver, near Hope, on the west side of the mountains and uncomfortably close to Puget’s project. 
Puget's seismic consultant, Bechtel, countered with a report that featured the big slide at Entiat, the one, they said, that blocked the Columbia River on the night of December 14, 1872.  There was native oral tradition of such a slide and the engineers knew that only a big shocker like '72 could cause such a signal event.  There was also a pattern of aftershocks that pointed to the Ribbon Cliffs epicenter, at a place called Earthquake Point.

That was all very compelling unless you happened to be the Washington Public Power Supply System and you were building a clutch of nuclear plants near Richland.  Suddenly, the big earthquake that was 300 hundred miles away and across the Cascade Mountain Range was located just 120 miles distant up State Highway 97. 
In 1872, people had no technology to measure the intensity of an earthquake.  In fact, a measure of our pre-Hydro-Thermal seismic maturity is that there were just three seismographs in Washington and three in British Columbia as late as 1969.   The Pacific Northwest Seismic Network has a different story today, thanks, in part, to our Hydro-Thermal friends.

We understand an earthquake that happened long ago by using one of the oldest technologies available to us, the observations of people describing what they see, hear and feel.  The tool is called the Modified Mercalli Scale and it has a twelve level description of an event, starting with something that might be felt on the second story of a wood frame building (II), to something that feels like a passing truck, or maybe some dishes rattle (IV), to something felt by everyone inside and outside the house with people unsteady on their feet, scared, with pictures falling off walls (VI).  (USGS Description)
Seismic monitoring today
These felt events are researched and plotted throughout the region, using newspaper accounts, diaries and oral communications. Many are related by the person who experienced it but also sometimes recounted second, even third hand.  There were few people in the parts of the Northwest that harbored the epicenter of 1872, but its effects were felt over the entire Northwest.  One man in Olympia, a steamboat captain named Lawson, had a watch perched on his vest pocket and looked at it when he felt the first bump:
"Shock occurred precisely at 9h.40 1/2m P.M.  It commenced with a light movement, gradually increasing for 18-20 seconds.  Then came the heavy shock, lasting four or five seconds; then it gradually decreased.  In six minutes after the first shock there was another, followed by two others one minute apart."
For every seasoned observer like Lawson, there was a man like Mr. McBride, a rancher, who with a partner had a spread three miles from the mouth of the Wenatchee River.  Their narrative was reported by the Portland Herald, many weeks after the event:
"They immediately sprang from their couch and were about donning their clothes when they were thrown to the floor in a rather sudden manner ... He turned to his partner and hastily informed him of his options, advising that they should leave." 
The more McBride observed, the greater the saga.  Soon, mountains were collapsing about him, rivers rose several feet in a few minutes and a great noise in the mountains, like the "simultaneous discharge of artillery," rattled the night. 
Research on McBride also showed that he was awaiting trial in Yakima at the time of the earthquake and had several convictions in his past.  He was convicted of selling liquor to the Indians after the earthquake, put in jail in Yakima, but broke out and fled to Canada.  Whatever his veracity as a witness, researchers apparently believed he had been thrown off his feet, a characteristic of a Modified Mercalli VIII, which they set as the intensity at Wenatchee.  
Soon after Bechtel's report, a team of scientists representing the WPPSS nuclear project began picking away at the theory that the landslide at Ribbon Cliffs occurred at the same time as the earthquake. 
They presented evidence based upon ash falls from two different St.  Helen's eruptions that the slide could have occurred as much as 100 years before the 1872 quake or, within a 14 year band before and after 1872.   In addition, they asserted that the real cause of the slide was not the earthquake but erosion at the foot of the cliff.

A Native American named Wapato John reported in 1891, 19 years after the quake, that he remembers the river filling up for hours after a big slide which he attributed to the earthquake. Notwithstanding Mr.  John, the new work done on the slide cause was helpful to the arguments of UW seismologists Malone and Bor who, in 1979, moved the epicenter west again, across the Cascades, near Ross Lake, 50 miles North of Puget's project.

Enter University of Washington Professor Howard A.  Coombs.  Coombs was the emeritus Chair of the University of Washington's Geology Department and possessed vast experience working on many of the Columbia River dams as well as in Japan, where he served as the geological advisor to the Supreme Allied Commander, Douglas MacArthur.  He had just closed out his service as head of a special panel investigating the causes of the Tieton Dam disaster when he was asked once more to lead a panel of experts, this time to figure out where the 1872 earthquake was centered.
It was an artful settlement, described by Eric S.  Cheney, Emeritus Professor of the UW College of the Environment, as: 
"The utilities subsequently convened a 'blue ribbon panel' that placed the epicenter between Earthquake Point (Ribbon Cliffs) and Hope -- east of the crest but sufficiently distant from Hanford."
Just one of the nuclear plants remain, but the fascination with 1872 remains.  A group of USGS scientists had another crack at the earthquake in 2001.  They moved it north and a bit and east, about 20 miles from Entiat at the south end of the lake, near the city of Chelan.  There it slumbers, trembling, until the Chelan Chamber of Commerce hires its own geologist.


As always happens when doing research, you find a couple of gems. 

First, there is UW Professor Eric S.  Cheney's Northwest Geological Society's Field Trip Guide Book #24 called "Floods, Flows, Faults, Glaciers, Gold and Dneisses, From Quincy to Chelan to Wenatchee."  It's a gem that will allow you to follow specific roads and road miles to some of the geologic miracles that he describes.  It's loaded up on my hand held for my next trip east.  (Cheney's Field Trip)

Second, there is the General Accounting Office June, 1967 report on the Hydro-Thermal Project.  It is an amazing documentation of the thinking at the time and how wildly off the electrical industry was and how much it has improved forecasting techniques.  (1967 GAO Report on Hydro-Thermal)


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