When I moved to Astoria almost a decade ago, I began to enjoy the pleasures of living on the edge of the continent, like the short trip to the beach, and the ever-changing weather. But when I attended a community meeting arranged by the Oregon Department of Geology and Mineral Industries this spring, I encountered a less appealing fact of coastal life: the prospect of a magnitude 8-9+ earthquake on the Cascadia Subduction Zone (CSZ) 60-90 miles offshore.
I considered myself fairly well informed about this fault over a mile below the surface, having researched it for my story “Deep Sea Exploration” published in NW Yachting in January. I described how manned and remote-control submersibles have made some amazing discoveries of volcanism and strange lifeforms where the Juan de Fuca plate descends beneath the North American continent.
But this meeting wasn’t about the wonders of the deep….the subject was the major earthquake the CSZ will create when–not if–it breaks, how to survive it, and how to escape the resulting tsunami that will hit the coast, in less than 30 minutes. A team of state experts has actually been working to educate coastal inhabitants on this topic for several years, but the reason for this program was, of course, the devastating Japanese earthquake of March 11. The pictures of large boats and even small ships thrown up into city streets shows that this is a topic of vital interest to all boaters.
Here in the Pacific Northwest, we also live on the “Pacific Ring of Fire”–as the 6.4 quake off Vancouver Island on September 9 showed. Luckily, this latest reminder did not cause any wave action, although the shock was strong on the sparsely inhabited outer coast. However, this barely compares with a local event on the Gulf of Alaska in 1958 that generated a short-lived wall of water about 1700′ high.
Lituya Bay, Alaska’s “Tsunami Alley”
Lituya Bay, seven miles long and two miles wide, is situated on the Fairweather coast of Alaska, and is the first inlet north of Icy Strait and Glacier Bay, providing the only secure anchorage for more than 100 miles in the Gulf of Alaska between Icy Strait and Yakutat. It has been swept by six tsunamis in 150 years. This incredible record is caused not by tectonic forces lurking far below the sea floor, but by simple landslides. The mountain side at the head of the bay is monumentally unstable, and has continued to peel off one huge landslide after another, making this the most thoroughly examined tsunami zone in the world. Not surprisingly, it is uninhabited.
Some of these slides may have been spontaneous, but In 1958, a 7.7 earthquake shook the entire region and caused a huge slab of the mountain to fall into the T-shaped end of the inlet. You could think of it as the perfect “geological storm.” It generated an unimaginably tall wave that raced across the mile-wide cove, crashed into the cliff and swept away the forest leaving only bare rock to a “splash” height of 1700.’ Miraculously, the crews of two of the three fishing boats anchored at the seaward end of the bay survived this calamity.
How to Survive a “Mega” Tsunami
The entrance is extremely narrow with tides running up to 13 knots and according to the Pilot should only be attempted in the short period of slack water on the bar—some 10 to 20 minutes. But the bay is the closest anchorage to the popular Fairweather fishing grounds, and on July 9, 1958, three trollers had anchored there because the fishing had been poor. It was a sunny evening, the water was calm, and the crews on the Edrie, the Badger and the Sunmore had no suspicion of what was to happen.
By 10 p.m., Howard Ulrich and his 7-year-old son, Junior, were in their bunks in the 38-foot Edrie, although it was still daylight. At 10:15 p.m. the boat began to shake violently as the water in the bay reacted to the quake. Ulrich reported hearing a deafening crash at the head of the bay. He stood on deck trying to see what had happened through clouds of dust.
After a couple of minutes, he realized there was an enormous wave heading down the inlet. He was slow to react until he realized he was observing: a wave around 300 feet high rolling over Cenotaph Island some two miles away. He leaped into action, putting a life jacket on his son, and starting the engine. He was unable to raise the anchor before the wave picked the Edrie up, but as it rose, the chain snapped and they were freed.
Ulrich had the discipline to grab the radiophone and yell “’Mayday! Mayday! This is the Edrie in Lituya Bay. All hell has broken loose in here. think we’ve had it. Goodbye.” He later estimated the height of the wave as 50 to 75 feet high His boat was swept over the south shore by the wave, then deposited back in the center of the bay by the backwash. The waves continued bouncing around the bay for half an hour before the situation eased.
Around 11 p.m., Ulrich started his engine and motored out to sea. He sent out another message saying he thought they’d made it through. Immediately, other boats on the outside began radioing back. But there was silence from the Badger and the Sunmore. Ulrich quit fishing a year later. He wrote a brief story for Esquire magazine entitled “What it Feels Like to Survive a Tsunami.” He continued to be effected by his narrow escape for the rest of his life.
On the Badger, Bill Swanson was also shaken out of his bunk. From his anchorage, he had a clear view of the head of the bay and the landslide. He reported seeing the Sunmore just about to turn out into the entrance when it was caught by the wave, flung over Harbor Point. Out of his sight, it quickly sank and the Wagners were lost.
The Swansons were more fortunate. The Badger, still at anchor, was lifted up by the wave and carried over the La Chaussee Spit at the entrance of the bay, stern first and riding the wave like a surfboard. Swanson reported looking down at the top of the trees, and estimated the height at about 80 feet. The wave broke and the boat hit the trough and began taking on water. They were surrounded by acres of wood debris – including a large tree that smashed through the pilot house and broke several of Swanson’s ribs – but they managed to get into the 8′ skiff wearing only their underclothes. Just before midnight, they were found by the crew of the FV Lumen who were searching through the miles of debris. (On the night of May 26, 1962. Bill Swanson returned to Lituya Bay for the first time. While there, he suffered a heart attack and died.)
Narrow Escape of Canadian Climbers
An hour before the wave struck, a seaplane took off from near Cenotaph Island (so named after the drowning of the 20 French sailors in 1786). On board were 10 Canadians who had just returned from the first Canadian ascent of Mount Fairweather. This was a day earlier than scheduled because the RCAF pilot was worried about fog. Another party of climbers was due that day by boat but they had been delayed.
Analysis of the Great Wave
The quake was later determined to be an 8.3; it was felt as far away as Seattle. At least forty million cubic yards weighing ninety million tons fell into 800 feet of water. The sound was heard 50 miles to the north. The weather also played a role as the bay gets up to 150 inches of rain a year. At Yakutat, 80 miles to the north of Lituya, three people out berry picking died when a small island they were on immediately dropped more than two dozen feet under the water. Later measurements determined that a nearby mountain had risen more than 50 feet at the same time. Overall, the earth had moved some 21 feet horizontally and 3.5 feet vertically along most of the fault line.
The French explorer Jean Francois de Galaup, Comte de Laperouse who is credited with the discovery of the bay in 1786, commented on the lack of trees and vegetation on the sides of the bay, “as though everything had been cut cleanly like with a razor blade.” He lost 20 of his sailors who attempted to row a longboat through the tide rip. Tlingit oral tradition contains several stories of giant waves and mass drownings in the bay. In 1936, a huge wave that uprooted and broke trees off as high as 500 feet around the bay, destroying evidence of previous smaller inundations.
A Distant Tsunami Will Arrive on the NW Coast in a Few Hours
Experts in the Pacific Northwest agree that the first step in tsunami awareness is to distinguish between distant and local tsunamis. A local tsunami originates in a seafloor fault close to shore, a distant wave travels across the ocean from Asia, Alaska or Hawaii. On March 11, 2011 a moderate distant tsunami crossed the Pacific from Japan moving at the speed of a jetliner and reached the US west coast 9 hours later, causing serious damage on the Oregon-California border in Brookings and especially Crescent City, which is extremely vulnerable because of a local seafloor fault that runs west from the shore. A series of 8-foot waves tore out the moorings and swept fishboats and yachts into a tangled mass, sinking many. But it could have been much worse.
Even a distant quake in the western Pacific or Alaska can generate a much bigger tsunami that will flood all the low-lying areas of the west coast. This happened in 1964 when the 9.2 Anchorage earthquake caused the largest and most destructive tsunami on record to strike the mainland U.S. Along the Washington coast, waves well over 10′ destroyed houses, cars, boats, and fishing gear. The tsunami continued south, wrecking many Oregon harbors, then pounding California. Crescent City was hit by a 21′ wave that killed 10 people, destroyed 289 buildings, and crushed 1000 cars and 25 large fishing vessels. A tank farm near the port burned for several days.
The only comparable geologic event in the northwest since then was the eruption of Mount St Helens in 1980. I witnessed the mushroom cloud of volcanic dust that rose to 60,000′ and remember news film of the angry land owners arguing with police at road blocks shortly before the explosion that took the top off the mountain. Volcanoes usually give some warning signs of an impending eruption, but earthquakes do not!
Today at the coast, with all the effort put into the international tsunami warning system with offshore buoys linked by satellite, forecasting has improved immensely, and the outreach effort—including sings, sirens and maps–means people living in coastal areas should be better informed. Those living in an inundation zone should be prepared to move to higher ground if the sirens sound. Note that an official Tsunami Watch is not an invitation to go down to the beach and “watch the tsunami.” This proved fatal to one uninformed spectator on March 11.
A Local Tsunami Could Arrive in 15 Minutes!
A local offshore quake and tsunami originating in the CSZ is an entirely different kettle of fish, and presents a far more deadly threat–one that is still not appreciated by the majority of the population. This is partly because of general apathy, the possibility of false alarms, and the fact that this prediction is based on new science. The revolutionary theory of plate tectonics that explained continental drift was not published until the mid 1960s.
The first evidence of a previous local tsunami originating off the northwest coast was gathered in 1987 by a Seattle geologist named Brian Atwater, working for the U.S. Geological Survey. He surveyed coastal lagoons by canoe, and identified sunken forests and isolated sand layers in soil profiles—all evidence of a tsunami. His research eventually led him to Japan, where he was shown contemporary records that noted a tsunami on January 26, 1700 without any earth tremors. (This also appears to be the source of Native American oral traditions describing a great coastal flood.)
Teams of researchers have continued this work and found deeper sand deposits and tree rings indicating over 40 great CSZ earthquakes during the last 10,000 years, spaced at intervals of 200 to 800 years. The good news is that Cascadia has been relatively quiet since 1700, so why worry? The bad news is that the Juan de Fuca plate grows by about 1 ½” of new seafloor every year, and after 400 years, that amounts to about 50 feet of new seafloor.
Theoretically, this excess seafloor may have caused a minute rise in the seabed until it dips under the North America plate at the CSZ. The best scenario is to have a steady slow motion movement over the centuries accompanied by a stream of small fairly harmless tremors. Unfortunately, what we have now is the opposite, a situation geologists describe as a plate that is “stuck.” When tectonic plates get stuck, pressure builds. Regular GPS surveys show that Highway 101 is rising over an inch a year.
The longer the wait, the bigger the quake. The latest research now suggests there is a 37% chance of the “Big One” hitting in the next 50 years, followed by a local tsunami of significant size. At the coast, the quake will probably do less damage than the tsunami, the opposite will be true inland. Everyone less than 50′ above sea level will need to move to high ground immediately. Having an emergency kit packed and a family rendez-vous arranged will make this easier. While the harbors of the Salish Sea are protected from the worst effects of a tsunami, the Strait of Juan de Fuca, the San Juan Islands are not. For boat owners, no matter where you are, this is not the time to check your mooring!
Distant Tsunami Awareness for Mariners
At sea: If you hear about an approaching tsunami, head for a depth of 50 fathoms or greater and monitor your radios for specific instructions from port authorities or the Coast Guard. Consider that you will be at sea for an extended period of time since tsunamis of varying size will continue for up to 12 hours. Carefully
manage all fuel, water, and other essentials. Port and marina facilities may be damaged upon return. If you’re in a smaller boat with a trailer in the marina, estimate how much time you have before the first wave strikes and decide whether you think you can get hauled out before the tsunami strikes.
In port: Your choices are to haul-out and leave, leave your boat moored and evacuate the zone, anchor upriver, or go to sea. The four factors to consider are the length of time before the tsunamis strike, local ocean and river characteristics, car and boat traffic, and the speed of your vessel.
At home: If you live in an inundation zone, you need to evacuate the zone for 12 hours. If you choose to deal with your boat at a marina, understand that you will be driving into an inundation zone under snarled traffic conditions and widespread confusion. You’ll need to negotiate heavy boat traffic and disarray in the marina, and on the river. Be realistic about how long it will take. Be sure to park your vehicle on high ground!
Local Tsunami Awareness for Mariners
You will have no question that it is the Big One. On land, intense shaking and earth movement will occur for four to six minutes, causing widespread destruction to structures, bridges, and roads.
At sea: If you’re at sea, you’re lucky. Head for a depth of 50 fathoms or greater and monitor your radio, Consider that you will be at sea for an unknown amount of time. Carefully manage all fuel, water, and other essentials. Your vessel may be essential in rescue and response efforts. When you return, expect dangerous debris in the water, limited facilities etc.
In port: You need to duck, cover, and hold on until it ends. After the shaking, you will have15 to 25 minutes to get to a site 50 feet above sea level. Do not return to or travel through the inundation zone for 12 hours. If you are just under way or in the bay, you won’t have time to get to 50 fathoms at sea. Your choice is to run aground and get to high land, or speed upriver. If you do go upriver, expect heavy boat traffic, huge ocean surges, and lots of debris. Several large deadly waves can appear for up to 12 hours.
At home: Duck, cover yourself from falling debris, and hold on tight until the shaking ends. After the shaking, you will have 15 to 25 minutes to get to a site 50 feet above sea level (if you are already above 50 feet, stay put). Stay there and help with rescues and recoveries. Do not go back into an inundation zone to check on your family or boat for 12 hours.
Roads and bridges will be damaged and destroyed. Expect to travel on foot.
Expect to be on your own without professional help or outside rescue for several days.
Food and potable water will be in short supply.
Structural fires will be widespread. Aftershocks will be common.