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Sunday, October 28, 2012

WAS THE LATEST CANADIAN EARTHQUAKE A WARNING?

Last night, as I was getting settled after a fine dinner, there came this sudden and piercing sound from my TV set, a warning message from Civil Defense, alerting the viewers about an incoming tsunami.  At 7:07 PM Hawaii time, a 7.7 moment magnitude (MM) earthquake struck the Queen Charlotte Islands of British Columbia. A tsunami was generated. I heard the sirens!

Twenty months ago I reported in the Huffington Post on the tsunami generated by the Chile 8.8 MM earthquake. Hilo, in particular, was concerned because the 1960 Great Chilean Earthquake of MM 9.5 (the greatest in recorded history) generated a 35 foot tsunami and killed 61.  Interestingly enough, I posted this article from my hotel room in Amsterdam, for CNN fed me the unfolding story, including live webcam views of both Waikiki Beach and Hilo Harbor. Many of my friends in Hawaii fled to the hills and were out of communication.

Well that tsunami only attained a height of two feet because the 8.8 MM earthquake was less than one-tenth as powerful as that 9.5 MM earthquake. For details on how to calculate the difference between any two earthquakes, click on "A Few Things You Should Know About Earthquakes."

Then, on 11March2011 I was in Japan and reported on how I had to contend with that Great Tohoku 9.0 Earthquake, Tsunami and Nuclear Disaster. Just some recent history to lead you into the present.

Should Hawaii have been concerned about this 7.7 MM from Canada, their largest since 1700? My first thought was that the epicenter sounded awfully close to that feared Cascadia Subduction Zone (CSZ), and, in fact, when I Google-checked, that 1700 quake was called the Cascadia Earthquake.  How imminent and serious is a mega-earthquake from the CSZ? Oregon and Washington would be crippled. However, all indications are that the Queen Charlotte Fault is not connected to the CSZ.

Anyway, about this latest, I suspected the tsunami would not amount to much because the energy released by this 7.7 tremor was all of 45 times weaker than the 8.8 of 2010 and 500 times less energetic than that world record 9.5 of 1960. Scientific sense told me that that the tsunami would be no more than a foot or two.

But you never know, for Canada is closer to us than Chile, so it would have been idiocy to go for any late night swim or await the incoming surf on a board, which, of course, some did. Certainly, it was only smart to keep away from beaches and the coastline.
However, signs from early deep ocean gauges, called DART buoys, seemed to indicate that the tsunami height might be higher than what would normally be expected from a 7.7. How high? Four to six feet on the newscasts, which is significant and potentially damaging. It was almost like some Hollywood screenwriter expanding the truth for the sake of drama. The later explanation is that there are so few earthquakes from this location that the only gauges they could refer to were peripheral.

Specifically, Kahului Harbor on Maui faced the incoming wave, Hilo was also somewhat in the path, the windward side of Oahu would be exposed and the east side of Kauai had to be careful. Then, oh great, at 10:28 PM when the wave was to strike, there were people walking around near Waikiki Beach on a live TV webcam, and there was no one around to chase them away because the police and fire staff had already evacuated.

While Waikiki is on the other side of the Oahu, if the tsunami is major, there is a wrap-around effect. Plus, a five foot tsunami wave is totally different from a normal five foot wave. The tsunami wave stays 5 feet high for hundreds of yards. Finally, the second to sixth wave can be even higher than the first. While some early projections hinted that the tsunami was specifically headed for Hawaii (graphics to the left used by local TV stations--something that I found hard to believe), this information appeared to be provided by the scientific authorities being interviewed, so there had to be some authenticity.

Well, it is the following morning. No one died, there was minimal damage and some excitement. BUT, COULD THIS 7.7 CANADIAN EARTHQUAKE JUST BE A TEASER FOR A 9.0 CSZ, as this fault is very similar to that of the 2004 Indian Ocean tragedy and 2011 Tohoku cataclysm? To quote:

...a 10% to 14% probability that the Cascadia Subduction Zone will produce an even or magnitude 9 or higher in the next 50 years.

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Sandy is still a hurricane at 75 MPH, and is still scheduled to bring wind, floods and snow to the the northeast part of the USA. My posting of 25October12 provides details.

However, the latest tracking shows Sandy skirting south of New York City. We'll see in two days.

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