How To Survive A Cascadia-Sized Tsunami

How To Survive The Cascadia Tsunami

"Thirteen thousand people will die in the Cascadia earthquake and tsunami," reads Kathryn Schulz's now-infamous New Yorker article. "Everything west of Interstate 5 will be toast." Turns out a very similar event occurred in Chile 55 years ago. What wisdom can its survivors share with residents of the Northwest?

Chile's Big One

On the evening of May 22, 1960, a magnitude 9.5 earthquake struck 100 miles off the coast of Chile. It would be the strongest earthquake ever recorded.

The resulting tsunami waves were so strong that they reached as far as Japan, where they killed 138 people.

Their affect was obviously stronger in Chile. By the time the flood waters had receded, authorities counted over 2,000 bodies.

The closest town to the epicentre was Lumaco, which even today is home to just 11,000 people.

How To Survive The Cascadia Tsunami

A Chilean Model For Cascadia?

The similarities between Chile's 1960 quake and the future one along the Cascadia Subduction Zone are striking. As noted by the USGS, "Recently, it has been discovered that the Cascadia Subduction Zone, like the subduction zone off Chile, has a history of producing earthquakes that triggered tsunamis. The most recent of these earthquakes, in 1700, set off a tsunami that struck Japan with waves about as big as those of the 1960 Chilean tsunami in Japan."

"Both the 1960 Chile earthquake and the 1700 Cascadia earthquake were caused by sudden ruptures of long segments of subduction zones," continues the USGS.

Back in the 1990s, the US Geological Survey identified the similarities between these two subduction zones and realised Chile's experience could provide valuable lessons for residents of the Pacific Northwest. So, it set about collecting first hand accounts of the quake, tsunami and their aftermath from survivors. This article is drawn from that material.

Will You Survive The Earthquake?

"All the people in and near the town of Maullín, Chile, survived the biggest earthquake ever measured. The deaths in the area came later, during the tsunami that followed the quake," describes the USGS. 122 people in the town were subsequently killed by floodwaters.

Earthquakes happen. Floors or entire buildings collapse, the earth opens up and swallows you whole, gas lines break and start fires. They're awful, but they're also a known quantity. Buildings are built to withstand them (at least in the western world), children are trained in what to do and, at least in comparison, plenty of people survive them.

That is not the case with tsunamis. As demonstrated by the 2004 Indonesian tsunami, an unstoppable wall of water moves inland, driving boats and trucks and trees and other deadly debris before it, obliterating nearly anything in its path. That one killed 228,000 people.

Shulz, the author of the New Yorker piece, feels safe enough to continue spending her summers in the northwest, the area that will be affected by the earthquake. In her follow up bit about survival advice, she strongly suggests that readers avoid spending even one night in the tsunami inundation zone.

"Of the almost thirteen thousand people expected to die in the Cascadia event, one thousand will perish in the earthquake," Schulz writes. "The others will be killed by the tsunami -- and they amount to nearly one in five people who are in the zone when the water arrives. That's a grim enough figure that it changed my own beach-going behaviour in the Northwest. Go to the coast by day, for sure. But if you're staying overnight, book a vacation rental, hotel room, or campsite outside the inundation zone."

How The Tsunami Will Happen

With the subduction fault in question, the western plate is descending under the eastern plate pushing against it. Pressure is currently building up and, when the leading edge of the top plate breaks free and "springs" out to sea it will lift up above the epicentre, while back behind on land, the "bulge" that's built up because of the pressure will collapse, lowering the elevation of the coast. That uplift creates the tsunami waves, the collapse back on shore worsens their affects.

How To Survive The Cascadia Tsunami

The earthquake will not create just a single tsunami wave, but many. As described by this graph of the 1960 earthquake's impact on Hawaii.

How To Survive The Cascadia Tsunami

And this one of its impact on Japan.

A tsunami waves will not appear like Katsushika Hokusai's "Great Wave," rather, they appear as a general swelling of sea levels. The sea just moves inland, at speeds of up to 500mph, with inexorable force.

Tsunami Warning Signs

A tsunami wave may be presaged by a drastic fall in sea levels. This may not always be the case. In Cascade or elsewhere, if you feel an earthquake and you're by the sea, flee to high ground immediately. And stay there.

The USGS relates the experience of a Chilean family in 1960:

"Vitalia Llanquimán lived outside the village of Mehuín. Soon after the earthquake shaking stopped, a man on horseback told her that the sea had receded from shore. At first, Mrs. Llanquimán was not alarmed by this news, but her husband took it as a warning that the sea, when it came back, might surge inland. Carrying their two youngest children, the couple hurried up a nearby hill, where they safely remained during the tsunami."

Meanwhile, in Hawaii, authorities sounded coastal sirens to warn citizens. In Hilo Bay, there was a three hour gap between those first sirens and an initial, small wave. The USGS tells the story of locals who thought that signalled the danger had passed.

"Carol was at her family's house on low ground in Hilo when the warning sirens sounded. Carol's parents took valuables to a relative's house in Papa'ikou, a few miles northwest of Hilo, while Carol and her brother Ernest checked on a niece who was babysitting outside of town.   "Later, Carol and Ernest returned to Hilo after hearing on the radio that tsunami waves had already come into town and were only 7 feet high. On the way back, they met a police officer who told them that the danger had passed. Carol and Ernest went to a sister's house in a low part of town. Around 1:00 a.m., they began to hear a low rumbling noise that soon became louder and was accompanied by sounds of crashing and crunching. Moments later, a wall of water hit the house, floating it off its foundation. When the house came to rest, Hilo was dark because the powerplant had been knocked out by the same wave.   "Carol and her family survived the 1960 Chilean tsunami without serious injury. However, 61 other people in Hilo died and another 282 were badly hurt. These losses occurred, in part, because the warning sirens in Hilo on the evening of May 22, 1960, were interpreted differently by different people. Although nearly everyone heard the sirens, only about a third of them thought it was a signal to evacuate without further notice. Most thought it was only a preliminary warning to be followed later by an evacuation signal. Others in Hilo were unsure of how seriously to take the warnings, because several previous alerts had been followed by tsunamis that did little damage."

Fleeing the inundation zone is the most effective survival technique. And, once you have fled, stay there for hours, until it is assured the threat has passed.

Schwarz is also clear about this, saying, "The coastline of the Pacific Northwest is beautiful, and I definitely do not discourage visiting it -- so long as you choose places with accessible high ground and figure out in advance how to reach it. You'll be doing so on foot (the earthquake will leave roads impassable), so be realistic about how far you and your companions can walk or run."

Surviving The Flood Waters

Again, let's be clear, you do not want to find yourself here. If you are caught by surprise due to limited time between the quake and tsunami or are somehow rendered unable to flee, there may be some hope left. Let's look at how people caught in similar situations survived the 1960 tsunami, as related by the USGS.

Ditch Your Stuff:

"Mr. Atala entered this warehouse between the first and second waves of the tsunami that struck Maullín. Mr. Atala was probably trapped in the warehouse when the second wave of the tsunami washed the building away. His son, Eduardo, said that afterward his father was among the missing and that his body was never found. Some residents of the town say that Mr. Atala was briefly restrained outside the warehouse by his wife, who grabbed his hair before he finally broke away. Many in the town, spinning a cautionary tale about a wealthy man, say he entered the warehouse to rescue money. Even as Mr. Atala was being carried off by the second wave, his barn outside of Maullín was providing a refuge for some 20 people, saving their lives from the tsunami."

Don't Rely On Roads:

"Minutes after the 1960 Chile earthquake, René Maldonado rode his horse on the road from Maullín, Chile. During the ride, Mr. Maldonado's horse had to jump newly formed cracks in the road. The weakened road was soon severed by the waves of the tsunami that followed the earthquake, leaving channels too wide even for a horse to jump. Not all people in the area fleeing the earthquake and the tsunami were as lucky as Mr. Maldonado. Some had their routes of escape severed by tsunami waves. Shaking from the 1960 earthquake not only damaged roads but also caused landslides. In addition to blocking roads, landslides caused by the quake dammed the Río San Pedro in the foothills of the Andes about 40 miles east of the city of Valdivia, Chile. Later failure of this landslide dam unleashed a flood that covered parts of the city."

Climb Structures:

"The second wave reached the barn just as Mr. Navarro joined his family there. Along with 14 others, the Navarro family spent the night in the loft of Ramón Atala's barn, safe above the tsunami waters that ran beneath them."

Or A Tree:

"At least a dozen people near Maullín, Chile, survived the 1960 Chilean tsunami by climbing trees. However, others perished when the trees they climbed were toppled by the tsunami. Ramón Ramírez, 15 years old at the time of the tsunami, survived by climbing into the branches of a cypress tree (photo at right) on a plain west of Maullín. While Mr. Ramírez stayed safely in the cypress, the waters of the tsunami swirled about the tree. The water crested at 15 feet above sea level, reaching several feet above the tree's base. In nearby Quenuir, at the mouth of the Río Maullín, Estalino Hernández climbed an arrayán tree to escape the tsunami's waves. While he clung to the tree, the waters of the tsunami rose to his waist. Not far away, the onrushing water covered land 30 feet above sea level. Although Mr. Hernández survived the tsunami, he lost his 13-year-old son to the waves. Quenuir had 104 other victims, most of whom took to boats just after the earthquake and were caught by the first wave of the tsunami."

Cling To Floating Debris:

"Nelly Gallardo survived the tsunami that followed the 1960 Chile earthquake by clinging to a log. The earthquake struck while she was digging for clams on the shore more than 4 miles west of Maullín, Chile. Soon after the shaking from the quake stopped, she walked about 100 yards inland to a house that was more than half a mile from the nearest high ground. The next thing Ms. Gallardo recalls is floating on a tree trunk. She clung to this trunk until the next morning. For a time she heard a man's voice crying for help-his body was found later. At daybreak she was more than a mile from where the tsunami had swept her up. The tsunami included many waves, but Ms. Gallardo recalls only the one that set her adrift."

Advice For Boaters:

The NOAA states: "If you are on a boat or ship and there is time, move your vessel to deeper water (at least 100 fathoms). If it is the case that there is concurrent severe weather, it may may safer to leave the boat at the pier and physically move to higher ground."

"Damaging wave activity and unpredictable currents can effect harbour conditions for a period of time after the tsunami's initial impact. Be sure conditions are safe before you return your boat or ship to the harbour."

If you're lucky enough to survive unscathed, help others: Shulz states that in addition to the predicted fatalities, the number of injured and displaced will be far higher. "Another twenty-seven thousand will be injured, and the agency expects that it will need to provide shelter for a million displaced people, and food and water for another two and a half million."

There is now way FEMA or the military will be able to provide immediate aid to that many people, across such a devastated area. Survivors will need to rely on each other for that aid, perhaps for up to a month or longer. Such was the case in Chile:

"In the first weeks after the 1960 Chile earthquake and tsunami, Yolanda Montealegre provided shelter for 40 families in Casa Grande, her large home on the outskirts of Maullín, Chile. Ms. Montealegre left her house minutes after the earthquake and reached high ground in time to watch the arrival of the second wave of the tsunami that followed the quake. The next morning, she found Casa Grande in good shape, its ground floor dry. The families she soon took in were among the estimated 1 million Chileans left temporarily homeless by the earthquake and tsunami."