The Cascadia Earthquake

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It is the most powerful earthquake to occur in Canada in the past 1,000 years, and it would have an impact not only in what is now Canada and the United States, but across the ocean as well.

Earthquakes along the B.C. coast are nothing new. In fact, hundreds of earthquakes hit that region each year but the majority are so small they are not felt by humans.

Geologists have been able to determine earthquakes of the past, long before written records were ever kept. In the period from 15,000 to 12,000 years ago, there were 18 major earthquakes in the region. This was around the same time that the first Indigenous people were beginning to arrive in Canada.

Between 500 BCE and 500 CE, there were no major earthquakes, but there were three in the space between 500 CE and 1000 CE.

Over the course of the past 10,000 years, it is believed there have been 19 major earthquakes, occurring at a range of 200 to 850 years.

On Jan. 26, 1700 at about 9 p.m., a 1,000-kilometre section of the Juan de Fuca Plate experienced a megathurst earthquake that pushed the plate 20 metres, resulting in an earthquake that measured an estimated 8.7 to 9.2 on the Richter Scale. The earthquake was so strong it released the same amount of energy as the United States consumes in an entire month today. It was also significantly stronger than the earthquake that hit San Francisco in 1906.

Today, it is believed the earthquake caused five straight minutes of shaking along the coast.

At the time, there were about 250,000 people living on Vancouver Island and the British Columbia coast.

According to evidence based on Japanese records, it is believed that the earthquake took place at 7 p.m., sending a massive tsunami across the ocean towards Japan. The 1,000-kilometre section of land that moved ran from Vancouver Island all the way down to northern California. The displacement from the earthquake was 65 feet and it is believed the earthquake relived all the strain that had been building by a few centimetres per year until it reached 65 feet.

Looking back at that date, apart from the written records by the Japanese concerning the tsunami, there are only oral stories told by the First Nations of the region impacted by the earthquake. It is hard to pinpoint if they are speaking of the 1700 earthquake, but there are stories of a major event that was very destructive around this time. Based on the number of generations going back to tell the stories of this event, it has been pinpointed to between the late-1600s and early-1700s. One legend speaks of a large earthquake and ocean wave that destroyed settlements at Pachina Bay. The only community on that bay not to be wiped out was Masit, due to the fact it was 75 feet above sea level. One First Nations woman was told to be the only survivor from Pachina Bay, simply because she was away at Barkley Sound when it happened.

On the north end of Vancouver Island, the First Nations people have a story of a night-time earthquake that destroyed nearly every house in the community. Another settlement was destroyed by a landslide at the same time, according to First Nations oral tales.

Another legend tells of an Indigenous traveler who was in the mountains when he heard the songs and dances of two mountain creatures. He joined in with them and as they sang and danced they grew tired until the man kicked the drum. This caused the man to be inflicted with a disease called Earthquake Foot. Every time he took a step, it caused great tremors throughout the region and formed gigantic waves. These waves took many out to sea, and washed away several settlements.

Chief Louis Nookmis from Pachena Bay said in 1964, using the oral history passed down from the time of his great-grandfather,

“The land shook, a big wave smashed into the beach. They had practically no way or time to save themselves. At night, a massive wave cut through the darkness and every single person living in Pachena Bay was lost.”

The entire village was gone, and only those on high ground were saved.

Another oral legend states that the shaking continued for 20 hours. This was likely aftershocks that continued after the main quake hit.

One unidentified Indigenous man from 1860 said that the tide rushed up at a fearful speed. Annie Miner Peterson, an Indigenous woman said in 1910,

“My grandfather saw one of the old women who had been left alive. She had been hung up on a tree, and the limbs of that tree were too high up. She was just a girl when she fell from it. Her back was broken from it, and she had a humpback thereafter.”

The Yurok people said of the quake, “The earth would quake and quake again and quake again. And the water was flowing all over.”

They then went to the top of a hill, wearing headbands of woodpecker feathers, so they could do a jumping dance that would keep the earthquake away.

The Makah people said the water changed level so much that canoes were stranded in trees.

Chief Guujaaw of the Raven Clan said the stories of the earthquake typically had a moral included. One story was of a canoe passing by a strange village. The man in the canoe was soon pursued and rather than risk becoming a captive, the man in the canoe threw himself into the water and drowned. That night, the villagers were punished with a tsunami that destroyed their settlement, but also washed up shells on the beach of a rival clan, making the chief wealthy.

There is a great deal of physical evidence of an earthquake happening as well. There are several ghost forests of red cedars on the coast of Oregon and Washington, which were killed by the lowering of the coastal forest into a tidal zone by the earthquake. The outermost rings on these trees dates to 1699. Core samples done of the ocean floor also show debris from landslides in the Pacific Northwest and Lower Mainland around this time. The rings were also quite wide leading up to the last ring, which showed there was a sudden event that happened rather than a slow rise of the ocean.

In the 1980s and 1990s, scientists found that lands along the coast dropped suddenly and were covered in waves and mud. Delicate marsh plants that were alive were killed by the rapidly advancing seawater.

On the Japanese side of things, it is strongly believed that a large tsunami hit Japan about 10 hours following the earthquake. Japanese records describe waves that were six to 10 feet high, hitting the coast. Based on current research, it is believed the tsunami went two kilometers up a river and destroyed farmed fields, fishermen’s shacks, a government warehouse and salt kilns.

Reports of the tsunami are found in official reports sent to Edo and in private family sources and histories. None of these reports speak of an earthquake in Japan, which lends evidence to linking the tsunami to the earthquake in British Columbia. For some time, the tsunami was called Japan’s “orphan” tsunami because there was no local earthquake to trigger it.

The Bridge of the Gods, which is a natural dam that was created by the Bonneville Slide, is believed by some researchers to have been caused by the 1700 earthquake. Recent work using radiocarbon dating has found that the slide links to an event that occurred between 1670 and 1760, which would put it in place for the earthquake.

A lava flow eruption also occurred on the Tseax Cone, which is located near Terrance B.C., around the time of the earthquake. The lava flow eruption is cited to have occurred between 1668 and 1714, damming the nearby river and forming a lava lake.

As for that fault, scientists had believed that it was dormant up until 20 years ago when it was determined that it has magnitude 8 or greater earthquakes every 500 years or so.

Will the area see another large earthquake? It is believed that a magnitude 9 quake happens every 526. As for quakes that register 8 or higher, they happen every 234 years, which means the area is due.

Only time will tell.

Information for this piece came from Earthquakes Canada, Wikipedia,, CTV News, Capital Daily, Canadian Geographic, The Vancouver Province, Hakai Magazine, National Post, Victoria Times Colonist,

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