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Significant Earthquake and Tsunami Events

A 1-foot tsunami isn't significant, but this is a good reminder that bad tsunamis can happen out of the blue.



They apparently haven't located the source yet.

Chron.com, among others, took a look at the Gulf's tsunami risk after the recent Kamchatka megathrust quake. Submarine landslides are the black swans here, though this layperson can't discount a volcanogenic one someday from Kick-'em-Jenny or some other firehole -- people tend to overlook volcanoes as tsunami risks, but again, this is an extremely low probability for the Gulf.
 
Aha! It was a glacier collapse event.

bsky.app

Dr Dan Shugar (@watershedlab.bsky.social)

There are a tremendous number of icebergs in Tracy Arm following the landslide-triggered tsunami. The reason for this is that ~300 meters of the north side of South Sawyer Glacier broke off and disintegrated into many many smaller icebergs as seen in @planet.com imagery ⚒️ [contains quote post...
bsky.app bsky.app

Correction (my fault): It was a rock slope collapse onto a glacier. Details and links.
 
Some images from the site. The landslide did reach water, causing a tsunami that was "just a tad" more than 1 foot high by several tens of feet. Some people reportedly were in the area, including a couple of kayakers who were taken on a wild ride, but there were no casualties reported.

 
Tsunami evacuation towers in Japan are awesome. Per the tweet, these were finished four years after the 2011 disaster.



Don't think we have any of those here but I have read that OSU's new earth/marine science buildings along the coast are also built with vertical evacuation in mind.
 
The building collapse simulation is the third tweet. (More on the 1985 earthquake.)

X translation:

I got a surprise this Saturday. Mrs. María Malvina contacted me via Facebook about a video I shared years ago of the collapse of the Nuevo León building during the 1985 earthquake. Imagine my surprise when she told me that she was one of the survivors

One can spend an entire lifetime analyzing geologically and mathematically the Earth's phenomena, but it's always good to remember that behind all those terrible photographs there are stories of human beings like you and me.

This is the video that Mrs. Malvina was looking for.

This is the result of a research study conducted by Professor Yoshio Kaneko from Kyoto University, #Japon in 2011 on the collapse of the Nuevo León building in #Tlatelolco during the #sismo of 8.1Mw, #CDMX 1985. The objective of the research was to analyze the causes of the collapse and propose prevention measures for future disasters.

It is concluded that the collapse of the Nuevo León building was due to a combination of factors, such as the deficient building design, the poor state of conservation, the soil amplification effect, and the intensity and duration of the earthquake.In the video, yellow zones are observed that indicate the points where the columns were subjected to great stress, and orange zones that point out the parts of the structure that collapsed. The connection between these zones generated a domino effect that caused the total collapse of the building.Note: let us remember that many of the Tlatelolco buildings were reinforced after the earthquake; these modifications were not completed until 1990 in some cases.

 
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This NHK disaster reporter I follow on X got into a Nankai trough tsunami simulator (Japanese: on using the browser translator a popup told me that overseas readers will be unable to see the videos -- the stills and text are dramatic enough; just click "I understand" and the browser translation should proceed after that).

And it turns out that Japan has learned from sad experience how treacherous tsunamis can be in large cities -- as with pyroclastic flows, it isn't simply a "smash 'em up" scenario.

Browser translation:

...
First, Mr. Arikawa points out that the danger is a phenomenon in which the power of tsunamis increases in large cities.

" Current condensation It is called ".

When a tsunami flows into an area with a large concentration of buildings, the height and momentum of the tsunami increases in narrow alleys...

...

Another thing Arikawa points out is the danger of ''attacking from unexpected directions.''.

If we examine how tsunamis rush through a simulation that takes into account the height of the building, we can see that once a tsunami reaches land, it spreads out in all directions, weaving between buildings....
Click to expand...

Simply building stronger buildings in hazard zones isn't enough.
 
I have trouble navigating JMA pages sometimes, but this account I follow is helpful -- X translation is fast and good:



X: "Changes in sea level due to a tsunami are being observed! Those in areas where a tsunami warning has been issued, please evacuate to high ground or a high place. Do not approach the sea under any circumstances."

There also are injuries reported.
 
NHK page (Japanese; with browser translation comes the standard "overseas" warning; click and you're good to go).
 
They downgraded the tsunami warning, but per Reuters:

...
"There is a possibility that further powerful and stronger earthquakes could occur over the next several days," a JMA official said at a briefing.

Following the tremor, the JMA issued an advisory for a wide region from the northernmost island of Hokkaido down to Chiba prefecture, east of Tokyo, calling on residents to be on alert for the possibility of a powerful earthquake hitting again within a week.
Click to expand...

That's because of the risk of a Kuril Trough megaquale -- I only know about it because some of the knowledgeable people I follow discuss that now and then.

As this layperson understands it, the Japan Trench has various segments. The Nankai Trough is off Honshu and threatens many millions in and around Tokyo. It likely is building up for a release some time fairly soon.

The Kuril Trough is off Hokkaido. It gets much less international publicity but is equally powerful, as its Wikipedia page history section shows -- and it, too, is likely to let loose soon, according to those knowledgeable but unofficial people I follow on X. I haven't read up in detail on either Trough.

There is a long-standing slow-slip event off Chiba Prefecture, though. That got some coverage in 2024, including this. I'm not sure where the Kuril Trough leaves off and the Nankai Trough starts.

So today didn't go catastrophically, fortunately, but this needs watching: was it a main shock or a foreshock?
 
The coastal folks in Japan's Aomori Prefecture will have to stay on their toes for a while.

Per browser translation of this article (Japanese; click "overseas" notice to read):

...
Professor Toda said, "Because strain has been transmitted to the shallow end of the plate boundary, it is possible that earthquakes of a similar magnitude and magnitude 7 class to the December 8 earthquake will continue to occur. "Even if it is not a huge earthquake, the epicenter will be shallow, so it is quite possible that ground movement on the seabed will increase, causing a tsunami and triggering a tsunami warning," he said, urging people to prepare for tremors and tsunamis.

Furthermore, regarding the possibility of a major earthquake, he said, "After a magnitude 7 earthquake occurs, the possibility becomes increasingly low. However, very large earthquakes can occur a month later or a year later. It's important to maintain some level of awareness for a long time," he said.
Click to expand...

For most of us, high-end 6-pointers and 7-pointers seem majorly enough, but 8s and 9s are SO much bigger.
 
This amateur volcanophile near Popocatepetl (Mexico City/Puebla area) also has a pendulum seismometer, and he recorded his experience of today's 6.5 quake near Guerrero, which is some distance from Popo:



Cool!

Because of the Guerrero gap, it's always a good idea to watch this area, though I'm not sure if the rupture happened on the plate interface or in the subducting Cocos plate (it seems rather deep for the overriding North American plate).

Meanwhile, updates (Spanish) and a comment:

 
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