Part 4:Seismic Risks to CGS–What the NRC Doesn’t Want You to Know

Part 4:Seismic Risks to CGS–What the NRC Doesn’t Want You to Know

A long but very well written article on the seismic risks of CGS which affects as we have seen in other posts, Hanford and the world. Please take the time to read this entire post by Gar Smith. We will post this into 4 parts to make reading easier and a bit less overwhelming regarding the enormity of the problem we face with CGS.

New Discoveries about Historic Megaquakes

It turns out the geology of West Coast of the US has something uniquely in common
with the East Coast of Japan: The potential for massively destructive “megaquakes.”
Japan’s 2011 quake was triggered by an offshore “subduction zone.” In tectonic terms,
“subduction” takes place when one vast stretch of crustal plate suddenly thrusts
forward, shoving itself beneath another massive plate.

It takes a subduction zone to produce a “megathrust” earthquake. There is only one
subduction zone along the continental US, and it is located off the coast of Washington,
Oregon and California.

For eons, Washington State has been an earthquake campground — a convention
center for tectonic convulsions. The NRC was aware that shallow quakes were widely
distributed over Washington State, while deep earthquakes were mainly felt in western
parts of Washington and Oregon, but the possibility of a catastrophic magnitude-9
megathrust quake was not suspected until 1984 — the very year the CGS reactor
began operations.

“The interface where rocks jerk past each other in an earthquake, called the ‘rupture
zone,’ is immense,” notes PSR’s John Pearson. How immense? In her book, Full Rip 9,
Seattle Times science reporter Sandi Doughton notes: “A magnitude 9 subduction-zone
quake can rupture an area bigger than the state of Maine” — i.e., 35,385-plus square
miles. This could be an ominous portent for the CGS: The state of Maine is 190 miles
wide, which is nearly the distance between the ocean and the CGS’s reactor core.
In Japan, there had been a historic warning of the 2011 quake. A similar megaquake
had hit the same area in 869 AD. The 8.8 Sanriku quake struck the northern coast of
Honshu, causing major devastation across and region. And it would turn out that a
similar foreshadowing event had occurred along the West Coast.

A ‘Ghost Forest’ Haunts the Northwest

On January 26, 1700, a violent realignment of the 740-mile-long Cascadia Fault
triggered a 9-magnitude quake that shoved the West Coast several feet closer to Asia.
The upheaval sent a monster tsunami powering across the Pacific. Ten hours later, it
crashed into Japan, destroying farmlands and flooding warehouses stocked with rice.
The cataclysm was caused by the relatively tiny Juan de Fuca plate pushing eastward
and plunging below the North American continental plate. While transform faults like
California’s San Andreas can generate severe quakes as strong as 8.1, only subduction
zones can muster the size and length needed to trigger megaquakes.

The Cascadia monster-quake was unknown to the engineers who designed the nuclear
reactors on the California coast and inland in Washington State.

Like many scientific discoveries, the 1700 megaquake was revealed by chance. In
1984, a USGS researcher named Brian Atwater was paddling a canoe along the
shoreline of Willapa Bay, just north of the Oregon-Washington border. On this particular
day, an especially low tide had exposed an odd expanse of mud bristling with hundreds
of weathered stumps. Atwater correctly suspected the half-buried trunks were the
remains of a “ghost forest” that had been destroyed by an ancient flood. Tree-ring
evidence placed the date of the disaster in 1700 — the same year the massive tsunami
struck the coast of Japan.

Atwater’s discovery was soon reinforced by a report by Eric and Kanamori Heaton in the
Bulletin of the Seismological Society of America. The Heatons proposed that the
Cascadia Subduction Zone (CSZ) was capable of generating incredibly strong quakes.
Geologists quickly connected the geomorphic dots and deduced that the towering seawaves
that struck Japan in 1700 had been spawned by a massive earthquake along the
CSZ. The same event that ravaged Japan’s coast first obliterated the Willapa Bay
forest, dropping the continental plate several feet in a few cataclysmic seconds and
causing a Pacific Ocean tidal wave to flood the region. (And, remember, when we say
“dropping a tectonic plate,” we’re talking about a plate that can be 50 miles thick.)

The Heaton report spurred a flurry of new research into the seismic history of the Pacific
Northwest. By 1995, at least 86 new studies reported evidence that an active CSZ
existed offshore — running more than 700 miles from the top of Vancouver Island and
south to California’s Cape Mendocino.

Other scientists subsequently discovered that the devastating megaquake, while
unknown to the country’s best academic minds, was well known among the
communities of Indigenous peoples living in the Pacific Northwest. The cataclysm was
firmly embedded in the oral tradition of the Makah people. The story of the battle
between Thunderbird and Whale had been passed down over 15 generations. The tales
told of the night when the oceans vanished, only to return and surge halfway up the
mountain slopes.

In 2012, the USGS published a report by Oregon State University’s College of Earth,
Ocean, and Atmospheric Sciences that documented a history of 19 major earthquakes
(ranging from magnitude 8.7 to 9.2) that rocked the CSZ over the past 10,000 years. In
addition, examination of seafloor drilling cores uncovered evidence of 23 magnitude-
8.0-and-above quakes occurring in just the southern section of the fault. The study’s
lead author, OSU professor Chris Goldfinger noted: “If they happened today, [such
earthquakes] could have a devastating impact.”

Patrick Corcoran, a hazards outreach specialist with OSU’s Sea Grant Extension
program, found the discoveries troubling. “We in the Pacific Northwest have not had a
mega-quake since European settlement,” Corcoran said. “And since we have no culture
of earthquakes, we have no culture of preparedness…. Now that we understand our
vulnerability to megaquakes and tsunamis, we need to develop a culture that is
prepared at a level commensurate with the risk.”

Previous research had concluded CSZ megaquakes (capable of causing devastation
from Vancouver Island to California) occurred about once every 500 years but OSU’s 13
years of research also revealed that major earthquakes tend to strike along the
Cascadia every 240 years or so. While four so-called “Full Rip 9″ megaquakes are
known to have hit the Pacific Northwest between 2000-0 BC, the period from 0-1700 AD
registered five 9.0-plus megaquakes.

The OSU team predicted there was a 40% chance a major quake could strike southern
Oregon before 2062. “It has been longer than that since it last happened,” Goldfinger,
observed. “Frankly, it is overdue for a rupture.” (Note: The 250th anniversary of the 1700
mega-quake fell in 1950.)

According to Jay Patton, a co-author of the OSU report, if the region is not hit by a
Fukushima-style megaquake by 2060, “we will have exceeded 85 percent of all the
known intervals of earthquake recurrence in 10,000 years.” The odds are that any child
born after 1990 and still living in the Pacific Northwest will become either a victim or a
survivor of the region’s next monster quake.

The past decade has seen an increase in progressively larger tremors along the CSZ.
Even so-called “slow slip events” can put added strain on nearby sections of blocked
faultline rock and this could eventually trigger larger quakes. A computer model created
by Stanford Geophysics Professor Paul Segall suggests that it may well be one of these
“tiny” quakes that triggers the next magnitude-9 catastrophe.

And when it happens, some estimates warn that the pressures backed up behind the
North American plate will cause the Pacific Northwest to suddenly lurch 57 feet to the
West at the same time the coast drops three to six feet.

The impacts of such a large earthquake would be extensive and long-lasting. While the
worst damage would occur in the cities west of the Cascades, the impact of such a
monster quake would be felt far inland. Over a wide region, high-voltage electric
transmission lines, natural gas supplies, gas and fuel shipments would be disrupted for
months. It could take up to three years to rebuild damaged electricity transmission lines.
Recovery would be slowed by the fact that many damaged roads and bridges would
need to be rebuilt. The loss of reliable offsite power and fuel would cripple operations at
the CGS, compromising the safety of the reactor and stored fuel rods.

hanfordcgsmapWhile a megaquake could send a tsunami racing up the Columbia River, it would be
unlikely to advance more than a half-dozen miles. More troubling would be the danger
that ruptured dams upriver could release a deluge in the direction of the Hanford
Nuclear Reservation

Even at a distance, the resulting ground motion would rock the CGS reactor with a force
that could damage pipes, threaten the containment structure, or crack the stored fuel
pools, causing them to drain and ignite. Any of these failures could lead to a
Fukushima-style core meltdown and a hydrogen explosion.