Keep earthquakes in perspective

The threat of “The “Big One” is discussed periodically in the press, but B.C. is one of the safest places within the “Ring of Fire.”

The threat of “The “Big One” is discussed periodically in the press (The NEWS, Jan. 13, for example) but none of these accounts also state that B.C. is one of the safest places to be within the Pacific “Ring of Fire.”

The most dangerous parts are where plate tectonics have formed deep offshore trenches. Japan and Chile are examples. During the 20th century, Chile had about 80 quakes ranging from seven to 8.5 in magnitude. These areas also suffer from volcanic eruptions, which can be deadly.

The great water depths in the trenches allows for the generation of tsunamis, which can be particularly destructive against low-lying shorelines, as witnessed by events in Japan a few years ago.

There is no trench off western North America. The main feature here is a series of laterally moving (transcurrent) faults which run from western California up to the ocean west of Vancouver Island. About 20 years ago, the Candlestick Park earthquake, at magnitude seven, killed or injured about four hundred people.

In this area, the earlier quake off Campbell River was considerably stronger, and recently there have been a couple of biggies, of magnitude eight, off Haida Gwaii. None of these caused direct loss of life or significant damage.

The probable reason is that western California is composed of young soft rock while British Columbia has a base of hard, igneous and metamorphic rocks which transmit stress in a different way.

The waters off British Columbia are probably too shallow to allow significant tsunami development, and even passing ones, like that from the huge 9.2 Alaska quake, which drowned more than 100 people, and then passed down our coast to drown another 12 in California, did little damage here, other than at Port Alberni.

In short, we really have had it pretty good and hopefully will continue to do so.

Jim DrummondQualicum Beach

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