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Old 23-01-2018, 12:39   #1
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Earthquake Prompts Tsunami Warning See Illustration

Earthquake Prompts Tsunami Warning See Illustration

The following is an EXCERPT from the linked article. I am posting it here to illustrate how a tsunami would propagate across the Pacific Ocean (see illustration below). I also found the bolded statements interesting, particularly the mention of the 30 foot rise in the ocean near the epicenter of the quake. See article for more details. This is just an excerpt for CF reading.
___________

"A magnitude 7.9 earthquake in the Gulf of Alaska triggered a series of tsunami alerts early Tuesday from southern Alaska down the western coast of North America, prompting warnings in some low-lying communities for people to seek higher ground.

But initial fears that such a massive tremor could unleash destructive waves that could hit coastal Alaska or Hawaii or ripple farther out subsided within four hours. There were no immediate reports of injuries or property damage.

A tsunami watch issued early Tuesday for coastal areas from Washington state to California was canceled nearly three hours after the quake. Tsunami watches were also eventually canceled for the Canadian province of British Columbia and Hawaii, as well as advisories for southern Alaska after 4 a.m. local time (8 a.m. ET), according to the National Weather Service's National Tsunami Warning Center.

A buoy located 188 nautical miles southeast of Cordova, Alaska, recorded a wave of about 30 feet around the time of the earthquake, according to NOAA data. But the report appeared to be an anomaly and it was unclear if it was related to the quake.

"We know one of the buoys showed a significant water rise right next to where the earthquake happened, but the next buoy didn't seem to experience that," NBC News meteorologist Bill Karins said. "We don't know yet what this means. It could have malfunctioned. We just don't know at this stage. It's too early to tell."

https://www.nbcnews.com/news/us-news...hquake-n840111
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Old 23-01-2018, 12:44   #2
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Re: Earthquake Prompts Tsunami Warning See Illustration

According to CBC:

"This kind of earthquake was what is called a strike-slip earthquake," Wagstaffe said. "That means there isn't as much vertical displacement. So when you're thinking of these rocks on the ocean floor, it didn't punch up like some other earthquakes have."

Instead of the water being displaced upward and forward, this water was moved much less by the horizontal motion. A fortunate circumstance for anyone living along the coast."

Why B.C. and Alaska avoided a massive tsunami - Technology & Science - CBC News

But who really knows...it's a mystery :-)
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Old 23-01-2018, 23:45   #3
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Re: Earthquake Prompts Tsunami Warning See Illustration

There was SOME effect--six inches to a foot of water rise. We all evacuated out of Seward around 1am, and sat in cars or at local safe zones trying to estimate what could happen. With the noaa data limites by the us gov furlough, all we knew was the magnitude of the quake and the dozen or so aftershocks. One buoy near Kodiak had a 10m dip, and we were like...oh ****! But it turned out to be an anomalous reading.

I admit, I was confused by not getting a big wave. The magnitude and location were perfect for a doozy. I think we probably all got pretty lucky that it was a tranverse and not vertical displacement causing the quake.
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Old 23-01-2018, 23:57   #4
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Re: Earthquake Prompts Tsunami Warning See Illustration

The Tsunami Warning Center email also included this tidbit
Quote:
. * Boat operators,
* Where time and conditions permit, move your boat out to
sea to a depth of at least 180 feet.

* If at sea avoid entering shallow water, harbors,
marinas, bays, and inlets to avoid floating and
submerged debris and strong currents.
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Old 24-01-2018, 05:54   #5
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Re: Earthquake Prompts Tsunami Warning See Illustration

Quote:
Originally Posted by Meanderthal View Post
There was SOME effect--six inches to a foot of water rise. We all evacuated out of Seward around 1am, and sat in cars or at local safe zones trying to estimate what could happen. With the noaa data limites by the us gov furlough, all we knew was the magnitude of the quake and the dozen or so aftershocks. One buoy near Kodiak had a 10m dip, and we were like...oh ****! But it turned out to be an anomalous reading.

I admit, I was confused by not getting a big wave. The magnitude and location were perfect for a doozy. I think we probably all got pretty lucky that it was a tranverse and not vertical displacement causing the quake.
Thanks for adding your local anecdote.
I am glad it was not a damaging tsunami.
Lucky sounds right, given the magnitude and location.
The anomolous buoy reading is strange coincidence, eh?
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Old 24-01-2018, 05:55   #6
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Re: Earthquake Prompts Tsunami Warning See Illustration

Quote:
Originally Posted by Macblaze View Post
According to CBC:

"This kind of earthquake was what is called a strike-slip earthquake," Wagstaffe said. "That means there isn't as much vertical displacement. So when you're thinking of these rocks on the ocean floor, it didn't punch up like some other earthquakes have."

Instead of the water being displaced upward and forward, this water was moved much less by the horizontal motion. A fortunate circumstance for anyone living along the coast."

Why B.C. and Alaska avoided a massive tsunami - Technology & Science - CBC News

But who really knows...it's a mystery :-)
Thanks for adding the mention of the slip type of quake.
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Old 24-01-2018, 12:35   #7
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Re: Earthquake Prompts Tsunami Warning See Illustration

We evacuated in Sitka AK.
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Old 24-01-2018, 12:45   #8
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Re: Earthquake Prompts Tsunami Warning See Illustration

I live in Soldotna AK. I was still awake when the earthquake struck. It wasn't violent, just a slow rolling motion that seemed to persist awhile. I was inside my house on the 2nd floor (3 story) and noticed the walls seemed to move in a fluid motion. Crazy no? I monitored the National erthquake and Tsunami web sites for a couple of hours after because I have both semi coastal property here on the Kenai Peninsula and a son who lives in Hilo HI. The quake first registered 8.0 281 miles south of Kodiak, later to be reclassified as 7.9 then 8.2. 20 miles deep. I have felt lesser magnitude quakes that seemed more violent. The next day I was surprised to learn how many people slept thru it and didn't realize there was a quake.
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Old 25-01-2018, 11:34   #9
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Re: Earthquake Prompts Tsunami Warning See Illustration

There was a magnitude 5.8 earthquake off the coast of Northern California 0839 today. No tsunami expected as these are considered to be slip faults, too
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Old 25-01-2018, 12:04   #10
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Re: Earthquake Prompts Tsunami Warning See Illustration

IIRC there was some historical record found that a major earthquake off Japan (pre-1700's?) actually left major impacts in then-sparsely populated Alaska. No real surprise that it could happen again.

And there's been some speculation that if volcanic activity in the Azores resulted in a blow-out, the resulting tsunami would destroy major cities all along the US EAST coast.

Of course if you want to lose sleep, look into the "super caldera" that is located in the Yellowstone Park area. Or the New Madrid fault, in the quiet and boring interior of the US.

Its a wonder how geologists sleep at night.
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Old 26-01-2018, 13:03   #11
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Re: Earthquake Prompts Tsunami Warning See Illustration

The East Coast is susceptible to a wave caused by a Lahore slipping off the canary Islands resulting in a tidal wave 3 miles high washing inland as far as Chicago . It's over due now, just like the one threatening the west coast waiting to slip off Hawaii. It's over due also. "Live in interesting times",they say !
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Old 26-01-2018, 14:13   #12
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Re: Earthquake Prompts Tsunami Warning See Illustration

Canaries! Thank you.
I look at this on the bright side: After the flood, it will be no extra expense for everyone to rebuild far enough inland to avoid rising sea levels.
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Old 29-01-2018, 15:17   #13
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Re: Earthquake Prompts Tsunami Warning See Illustration

I think geologists sleep at night because they understand we are mere specks in the eye of geologic time 😜.
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