On February 10, 2005, a jam-packed Sam Gamble Hall at 615 Booth Street, Ottawa, welcomed Dr. John Clague, Professor and Shrum Chair in Science at Simon Fraser University, B.C., and one of Canada's leading authorities in Quaternary and environmental earth sciences. Dr. Clague's lecture was one in a series organized by the Logan Club, which was founded in 1887 as a forum for Geological Survey of Canada (GSC) staff and visiting scientists to discuss earth science topics.

Dr. Clague is no stranger to NRCan. For 25 years, 1973–1998, he was a scientist with the GSC and has 30 years experience in surficial/terrain mapping, Quaternary stratigraphic investigations, engineering and environmental interpretations of surficial geological information, and natural hazard studies. Across Canada, he is well known for his local, national, and international research collaboration with other geologists, geographers, biologists, and physicists.

While the official title for the lecture was "The Great Earthquake and Tsunami of December 2004 and Their Implications for the West Coast of North America", Dr. Clague put the topic more succinctly as "Can It Happen Here?" - and, according to him, it's not a matter of "if" but of "when".

A layer of clean sand, deposited by a landward surge of seawater at the time of the last great earthquake in1700, is sharply bounded by peat and mud in a pit dug at a marsh just east of Tofino on the west coast of Vancouver Island. [Photo by John Clague].

"It will definitely happen here," he said, "however, loss of life [compared to the 150,000 reported dead in the December 26 earthquake/tsunami] is expected to be two orders of magnitude less, due to Canada's social and economic differences". As some staff perched on tables and others sat cross-legged on the floor of the Hall, Dr. Clague presented a simulation computer model of the Southeast Asia earthquake and tsunami, as prepared by NOAA (the U.S. National Oceanic and Atmospheric Administration). The shock from the earthquake was bidirectional, creating waves that moved rapidly across the Indian Ocean to hit Sri Lanka and Thailand within two hours. The waves created by these types of massive, "megathrust" earthquakes are not ordinary, surface waves, he said, but are a result of a "ruptured sea floor" that disturbs the water column, creating highly energized "body waves". The energy of these waves can move at 600–800 km/hr, reaching their greatest velocity in deep water. In the shallow waters near shorelines, the velocity decreases. As a result, the crests of the waves bunch up and rise to accommodate the confined water, creating "an onward surging mass". An almost surreal photograph of this "surging mass" showed a crowd of beachgoers in Thailand running in panic from the 20-foot wall of water - the tsunami.

Dr. Clague emphasized that Canada has a lot to learn from the December 26 earthquake/tsunami, due to a number of similarities between the Sumatran plate tectonics and our Cascadia subduction zone on B.C.'s west coast, which lies within the "Ring of Fire". This huge ring of volcanic and seismic activity stretching from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands, and south along the coast of North and South America, contains over 75% of the world's active and dormant volcanoes.

The two areas share similarities in seismic potential, he said, including long intervals, i.e. hundreds of years, between great earthquakes; long subduction zones; strong ground shaking when these earthquakes occur; offshore fault areas; and similar plate tectonics. "Canada has had some of the biggest earthquakes on earth," said Dr. Clague. The last tsunami-creating earthquake on the West Coast occurred on January 26, 1700. Scientists have established that date based on anecdotal and stratigraphic evidence. Dr. Clague explained that by studying the marsh surfaces and tidal mud flats of the west coast of Vancouver Island, scientists can see abrupt changes in the stratigraphy, identified by a layer of clean sand sharply bounded by peat and mud.

The crowd in Sam Gamble Hall definitely did not want Dr. Clague to leave; they peppered him with questions for almost 20 minutes following the talk. And for good reason: Dr. Clague successfully presented the science behind the December 26 tsunami tragedy with empathy and passion, but, without being alarmist, also managed to raise awareness of our own vulnerability to this kind of major disaster.

For more information on the Logan Lecture series and to view abstracts of past lectures, visit the Logan Club. Wouter Bleeker and Andrée Blais-Stevens are the current co-chairs.

For copies of Dr. Clague's PowerPoint Presentation, contact Wouter Bleeker.