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Books Cascadia's Fault: The Deadly Earthquake That Will Devastate North America, by Jerry Thompson

On the B.C. coast, there are stretches of shoreline that lie buried under layers of bleached white and broken shells. Known as middens, such sites are archeological gold. They tell us that for thousands of years these were places where aboriginal people drew sustenance from the sea.

The deeper the layers of discarded mollusk shells, food remains, broken bits of stone tools and garbage, the further back in time such sites were used. At one midden near Namu, where a long-abandoned salmon cannery's wooden buildings now collapse into the sea and rot in the encroaching temperate rain forest, the broken shell fragments are nine metres deep; a sign that here, and for roughly 10,000 years, Kwakiutl people lived and thrived.

But episodic events of unimaginable violence have been preserved in stories and artwork. In one telling of the story, a Kwakiutl man dances, his face covered by a cedar mask. The mask's movable visor alternately covers and uncovers his eyes. When the dancer appears, everyone feigns terror. They know from their elders' stories that monsters strike without warning.

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The Kwakiutl earthquake mask was undoubtedly inspired by magnitude 9 or greater earthquakes, events completely outside the realm of experience for millions of people who now call the West Coast of North America home. Which is why veteran documentary filmmaker and writer Jerry Thompson has stepped forward with a timely warning of the monster that will - not may - strike again.

In 10,000 years of Kwakiutl occupation at or near Namu, some 20 magnitude 9 earthquakes have occurred, one every 500 years or so, quakes that ripped the entire length of what is today called Cascadia's Fault, a crack on the sea-bottom roughly 50 kilometres off of the north end of Vancouver Island and arcing southeast and then nearly due south to a point 1,100 kilometres away in northern California. It is here that the oceanic Juan de Fuca Plate pushes toward and underneath the North American Plate at a rate of 40 millimetres per year - about the growth rate of your fingernails. The colliding edges of the plates are locked, however, and when enough pressure builds, they slip suddenly.

We now know precisely the last time an earthquake of such magnitude occurred along Cascadia's Fault. On the far side of the Pacific Ocean in a country still reeling from one of the most violent earthquakes in modern history, a tsunami came ashore around midnight Jan. 27. In the seaport town of Kuwagasaki on Japan's north coast, the local magistrate recorded the odd event. Odd, in that while earthquakes and tsunamis were a well known fact of life, there had been no temblor prior to the giant wave crashing ashore, a 16-footer that instantaneously destroyed 13 homes, triggered a fire that burned 20 more structures and sent villagers fleeing to higher ground to escape the frigid waters and all the detritus being pushed at frightening speed their way.

One can only imagine in the absence of written records what the earthquake meant for residents just to the east of Cascadia's Fault in villages like Namu. But it would have been sheer terror: a violent upheaval of the oceanic plate, relentless shaking for five solid minutes, and then the waves.

Concentrating on the scientific sleuths that work largely outside the media spotlight, Thompson pieces together the equivalent of a seismological CSI, offering up one stunning revelation after another about what investigators have unearthed about such events. To the north of the Cascadia Fault, in 1964, a similar type earthquake - a 9.2 magnitude event - hoisted up as much as 200,000 square kilometres of seabed and deformed a land mass roughly the size of Washington and Oregon combined.

Meanwhile, out at sea, cores of seabed sediments have uncovered irrefutable evidence of landslides occurring simultaneously all up and down Cascadia's Fault at regular intervals. And on land, terrestrial evidence confirming the power and timing of the earthquake that sent a tsunami rocketing toward Japan at the speed of a jetliner has been deduced from counting the growth rings in the preserved roots of ancient dead cedar trees, showing that numerous such trees all died at the same time from one cataclysmic event.

The difference between then and now, of course, is that when a magnitude 9 quake next hits Cascadia's Fault it will simultaneously hit five major cities at once: Sacramento, Portland, Seattle, Victoria and Vancouver. If the vibrations from the shaking are of a low frequency, all bets may be off for hundreds of tall buildings that, as Thompson notes, are particularly vulnerable to such events. It was many of the taller, more modern buildings in Mexico City that fared so badly in the magnitude 8 earthquake of September, 1985.

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With so many cities hit at once, and with Canada having no equivalent of the U.S. National Guard and only a small dispersed military, residents surviving a magnitude 9 earthquake along Cascadia's Fault can expect to be on their own. The good news is that the overwhelming number of them will survive the event itself. It's the aftermath they'll need to be focused on, which means being prepared for an event that has a 30 per cent chance of occurring in the next 50 years.

In the aftermath of events 300 years ago, the Kwakiutl residents of Namu understood the need to heed such warnings. Will we?

Ben Parfitt is a resident of Victoria and a frequent writer on natural resource, science and environmental issues. He is the author of Forest Follies: Adventures and Misadventures in the Great Canadian Forest.

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