Pacific Quakes

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El and Bill

New member
"NWS TSUNAMI WARNING: PT. CONCEPCION-CA TO OR./WASH. BORDER: and AMCHITKA PASS-AK TO ATTU-AK: M8.9 NEAR EAST COAST OF HONSHU, JAPAN 2146PST MAR 10:". - USGS

There have been a number of large earthquakes off the east coast of Honshu Island in Japan for the past week. They have been far enough offshore so as not to cause damage.

This morning there was a larger quake and this generated the warning above - possible tsunami along the Pacific rim including northern CA and perhaps southern Oregon coasts. Unlikely to be large or destructive but good to be aware of possible hazard if you are on the coast this am

Also - not to alarm, but to perhaps inform - tsunamis are usually generated by shock waves at the epicenter being translated to sea waves in the ocean, but sometimes they are caused by submarine landslides triggered by 'land' waves from a distant quake. Also, regions under earth stress (usually along tectonic plate boundaries) are sometimes triggered to release and cause an earthquake far removed from the original quake.

In the past few weeks, there have been numerous small (richter 4-5) quakes off the Oregon coast - these quakes releasing stored energy, so are a good thing. But, a large quake (even as distant as Japan) causes a 'ringing' throughout the crust and if the offshore Oregon quakes have moved a plate into a locked position, the vibrations could release the frozen segment and generate a quake - which in turn could cause a tsunami.

This is not said to cause worry - only, to share geologic ideas as a caution. The early sign of an approaching tsunami, is often a sudden drop of sea level at the shore. The offshore buildup of a wave 'pulls' water from the shore - and the wave builds height and smashes on the shore. So - sudden drop in sea level along the shore - get to high land quickly.

Highly unlikely there will be any effects on our NW coast, but forewarned is forearmed - and the USCGS decided to warn so thot I'd pass it along to Brats in the area.
 
Bill thanks. This quake in Japan, although not the largest in the Pacific region in the last 60 years, (but massive) may become one that leaves the most lasting visual impact on us. I believe that there will be many videos of the quake, and as we have already seen, videos of the tsunamis in Japan. This quake happened during daylight hours, and there are more cell phones with video capabilities now than just a few months ago. Also, there will be many videos from stationary monitoring cameras. It will be chilling to watch.

One thing that I have not heard mentioned about tsunamis is that a coastal wave of say 3 feet, may be funnelled into bays that can concentrate and increase the waves energy. As I recall the waves from the Alaska quake of 1964 caused the most damage in coastal bays along the AK, HI, WA, OR and CA coastlines.
Also, the coastal waves will come in a series. HI has had a series of at least 4 waves. Don't go to the beach after the first wave! A 1 foot wave may not get you, but the logs that the wave moves can get you.

May all of us on the coast be safe!

Robbi
 
Bill - knowing of your considerable expertise with all things geologic, have you been following the debate on "bad moon rising", i.e., whether the proximity of the moon to earth (closer) can trigger earth quakes? Is there any thing to this or are these just random occurences?

John
 
John-

The relationship between the moon perigee (supermoon) and earthquake has been suggested by an astrologer. As far as I know, and from geologic sources i've just looked up, there is no scientific evidence to show a relationship - not to say there is none, but no scienctific data that I have read.
 
I don't know if every one is getting the same info but here in the SF bay area we are seeing significant damage to Santa Cruz harbor. It looks like most of the problems were from boats and docks in the back of the harbor.

I would suspect that the area in the back of the harbor rarely gets much from wave action so the docks and boats may not have been secured as well.

We are seeing several boats overturned, several floating in the surge and hitting other boats and docks. The vast majority of the boats are probably okay.

The surge of water looks like a strong river flow, maybe more than 10 knots at its peak. They have had 2 or 3 surges that last maybe 10 minutes of inflow. Much more than I expected to see in this area.
 
Bill - Thanks for your info. Here in White Suffering Springs, we have been experiencing very high winds the last several days. Gusts in excess of 90 mph have hammered us. But with the temperatures above freezing, we are experiencing the old time Chinook, and with the snow pack at 157 % of average, water is standing and running everywhere.
John
 
So what should one do if a tsunami warning is issued and you are out on your boat in, say, SE Alaska and no ports within range? I'm especially interested in what our AK members have been trained to do.

Warren
 
In S. Calif. I took our boat out to sea when there was a Tsunami warning. Alaska with fjords may be somewhat different. During the 1964 quake I went to about 4 miles. Once you clear of the coast.

There is damage to Santa Cruz harbor boats with only an 8" reported surge.

Places like Crescent City, Half Moon, Santa Cruz etc would be better off at sea. At sea there is only a gradual rise and fall of the water.
 
If I was in a potentially exposed harbour I for sure would put to sea, a few miles offshore is generally thought safe.
The Tsunami that clobered Hilo many years ago was obsered by fisherman from a little ways offshore as huge waves hitting the beach and hardley a ripple where they were offshore.
 
The quake and tsunami are tragedies and now there may be the danger of a melt down at one of the reactors. Their engineering to minimize earthquake damage is the best in the world. Lets hope none of our reactors ever get hit by a major quake.
 
If you get the warning early enough, and you can get underway promptly, and you can get into deep wide water, then put to sea.

If not, get to high ground. That may not be possible from an anchorage or isolated dock. In many places without roads, the forest is too thick to be able to climb up into easily, and if you leave your dink on the beach, it could be swept away. A long, shallow inlet could be the worst place to be.

In SE Alaska, the weather also is a concern. What are the conditions out in deep water?

I would say that leaving the boat in these circumstances would be similar to abandoning ship and taking the 'bail out bag' and a portable VHF and epirb would be important.
 
We are on the west coast of Maui. First waves came in at 3:15am. Tsunami sirens started going off hourly about 9PM. We headed up hill 6 blocks to one of the schools and slept in the car for several hours and then returned to the condo. No damage, no waves came above the beach, although some areas of HI did get some damage.
What is interesting is that there are still periods of the water receding and coming back to a little over normal level at 10 hours after the first wave. The tides here are normally only a couple of feet.
 
About 1:30 this morning, after the tsunami watch was changed to a tsunami warning, I headed out to the dock and set of for safer harbor further inland. (Went upriver to a 10% inundation area rather then out to sea due to the weather report for later in the day.)

Initially I felt that perhaps I was overreacting, as i didn't see any other boats leaving port, although it is often the case that you see wrecked marinas after a disaster, with most of the boats, now damaged, still there.

Then I got to the main channel for San Francisco bay and it was busy. So many large boats - container ships, tankers, work barges, and ferries - were moving rapidly on their way out to sea that I had to stop and wait a couple minutes for a break in the traffic so I could cross the channel and continue north.

Going up the Petaluma River at speed took an interesting bit of navigation as it is a dredged channel with slightly underwater mud flats to either side that winds back and forth.

Eventually got to where I was going, tied up, and caught a ride home with my father. What a night.

David
 
What I don't get is the news keeps saying that the wave travels 560 miles per hour
maby in the open water but on land? If you were hit by a wave at 560 mph I don't think there would be much left. The news people like to make it sound better maby?
 
I don't think the 'news readers' and 'news writers' have much of a clue. That high speed is for the open ocean. The wave took about 8 hours to get to the US west coast. 8 x 600= 4800 miles.
If the wave traveled slower it could not get to the US west coast in the 8 hours that it took.

In the open ocean the wave is just a few inches high. When the wave starts to 'feel the bottom' in shallower near shore waters, the wave trades speed for height.
 
I just saw the Fox news photo's of the waves hitting the Cresent Beach Small Boat Harbor and it wasn't pretty. I certainly hope that all C-Dory folks and their boats are safe and without damage throughout the West Coast. This boating website is very special, and the members are a great group of folks. Even though there appeared to be no people on the boats in the harbor, it sure pained me to see them tossed around like match sticks. My thoughts are also with the sailors and boaters in Japan. I didn't own any of those boats being destroyed, however, I watched with great sadness at the destruction of the boats as well as the loss of life!! :(. Safe boating, Jim
 
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