Blog dedicated primarily to randomly selected news items; comments reflecting personal perceptions

Saturday, December 27, 2014

Waiting For The "Big One"

"In some places there will be maybe 20 minutes before the wave hits."
"The gold standard is what was done in Oregon and that's what we should aim for."
"There is a very clearly defined set of tsunami problems that need to be solved."
Garry Rogers, senior research scientist, Pacific Geoscience Centre, Victoria

"There would be widespread damage, including thousands of injuries and fatalities and the destruction of hundreds of buildings."
"Overall the province [British Columbia] is still at a significant risk if a catastrophic earthquake were to occur today."
British Columbia auditor general report

The dreadful earthquake and following tsunami of horrendous proportions, took the lives of a quarter of a million people in fourteen countries on what was for those countries a truly fateful day in 2004 when Indonesia [200,000 dead, 37,000 missing], India [11,000 dead, 3,000 missing], Sri Lanka [31,000 dead, 4,000 missing] and Thailand [5,400 dead, 3,000 missing] suffered a tragedy of monumental proportions in the Indian Ocean tsunami.

A village near the coast of Sumatra lies in ruins
In the modern era, that incredible loss of life resulting from an upheaval deep within the bowels of the Earth's crust, leading to the aftermath of giant waves washing ashore, was almost matched in intensity by the 2011 earthquake that struck offshore with a 9.0-magnitude force, second to the Indian Ocean's quake that registered 9.1. Japan lies in a well-known earthquake zone; the country uses high-value technology to monitor such events, and the result was a still-considerable loss of 18,000 lives. The situation hugely compounded by a meltdown of five nuclear reactors.

This is an aerial view of damage to Sukuiso, Japan, a week after the earthquake and subsequent tsunami devastated the area in March, 2011.                                                       Credit: Dylan McCord. U.S. Navy

In the Pacific, where tectonic plates on the Cascadia subduction zone slide past one another on their 1,13-kilometre cascade, geologists say that a mega-thrust quake is inevitable. Killer quakes occur in the area every 500 years. It is now 300 years since the last one according to scientists who have found evidence of 19 giant Cascadia quakes in the past ten thousand years. Those experts now predict such a cataclysmic quake is possible in the next fifty years.

"We should be as well prepared as Japan", agrees John Clague, an expert from Simon Fraser University, in recognition of Canada's lag in mapping areas most potentially threatened by tsunamis and "seismic microzonation". Identifying pockets within cities and districts more prone to shaking, liquefaction and damage is vital to protecting the population living along the B.C. coast, particularly the vulnerable area of Vancouver Island.

TRANSITIONS - Pacific Rim National Park (British Columbia)
Pacific Rim National Park (British Columbia) (CNW Group/Transitions)

Like Japan and countries lying off the Indian Ocean, the West Coast of North America is vulnerable to earthquakes which regularly occur. No expert can predict with any reliability when the next large quake of magnitude 9 or more will occur, but they do stick with the 12 percent probability of a megathrust earthquake within the next fifty years.

When that happens, the ground will shake with an intensity sufficient to crack and collapse bridges and unreinforced buildings. Landslides will occur, cutting off roads, railways, and leaving millions of people without power, water, telephone service. A wall of water will race ashore to flood out of existence resorts, campgrounds, and any kind of human habitation, while altering shipping channels and severing major undersea cables.

And now the auditor general of British Columbia has launched a full critical review of Emergency Management BC, responsible for the response to such catastrophes, which has failed to treat the issue as a priority; devising comprehensive plans to deal with the possibility of an immense quake and the following tsunami to make certain that as many people are alerted, to head for shelter on high ground, as possible.

While North America is not likely to experience the intensity of a phenomenon leading to the horrors that resulted from the Sumatra quake, a major disaster could still develop. Emergency planners in B.C. and the U.S. consider it likely that deaths could exceed 10,000, with another 30,000 injured. Aging buildings and infrastructure in Victoria, Vancouver, Seattle and Portland are clearly at risk. Damage, should such a quake and tsunami occur, is estimated to cost Canada up to $75-billion.

A metres-height tsunami crashing ashore and racing up inlets would destroy coastal communities, fish farms, resorts and logging operations. A detailed analysis superior to anything that has as yet been undertaken is required to understand where the giant waves, capable of travelling at jet-flight speed, might break land, to result in the most damage. Inlets and channels are capable of amplifying five-metre walls of water for maximum destructive effect.

Canadian geologists point to the work by the state of Oregon in this direction, where tsunami inundation zones have been mapped out in detail to enable communities to plan evacuation routes, and identify and shape safe havens for people to flock to. And at the same time work on devising methods for the reinforcement of coastal highway bridges to withstand such a tsunami.

westcoast_quake_wordpress (1)

Five-metre waves, which are expected to result from a Cascadia tsunamis, while potentially destructive are not quite the threat seen by the size of the 40-metre monster waves the Tohoku quake off the coast of Japan presented in 2011. Canadian scientists feel it is necessary that sensors be placed on the sea floor along the Cascadian fault for finer estimates of tsunami wave heights. Japan has done just that off their coast.

"We know the on-land measurements, but we don't know what is happening under the water. That is the important part for tsunamis", according to research scientist Dr. Garry Rogers. Living in a wonderful country in a province with breathtaking and varied landscapes does have its risks as a result of natural geology for which the province is justifiably famous.

Credit John Clague

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