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Tsunami & Mega-Tsunami

‘Major Tsunami Warning’: Japan Evacuates Coastal Areas After 7.6 Magnitude Earthquake​


People living on the coast in north-central Japan have been ordered to evacuate to high ground after a large earthquake struck the Noto Peninsula on Monday afternoon, with the government warning of a potential five-meter (16-foot) tsunami.

A 7.6 magnitude earthquake struck the Noto Peninsula in Ishikawa Prefecture, the central region of Japan’s main island Honshu, around 1600JST (0200EST, 0700 GMT), the most powerful earthquake in that area since records began. Japanese state broadcaster NHK is telling citizens: “The tsunami has already arrived. Please run away as soon as possible… Please remember the Great East Japan Earthquake. Please run away as soon as possible to save your life”.

Update 0645EST: ‘Major Tsunami Warning’ downgraded for Noto

Some good news, perhaps, the urgent “major tsunami warning” issued for the Noto Peninsula, under which the 7.6 magnitude earthquake struck during Japan’s Monday afternoon has been downgraded to a “tsunami warning”, with the expected wave height falling from five meters to three meters. The evacuation order is still very much in place, however...

https://www.breitbart.com/europe/20...-magnitude-earthquake-strikes-central-honshu/

maximus otter
 
Frideswide said:
was it a similar event that triggered the fukashima disaster?
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Not quite the same, I think. The Fukushima Disaster earthquake originated in the sea, whereas this one originated on land.
Different effects on the sea's behaviour, even though this one was a 7.6 on the Richter Scale.

At least, that's what I think. Anybody correct me if I'm wrong.
 
Mythopoeika said:
Not quite the same, I think. The Fukushima Disaster earthquake originated in the sea, whereas this one originated on land.
Different effects on the sea's behaviour, even though this one was a 7.6 on the Richter Scale.

At least, that's what I think. Anybody correct me if I'm wrong.
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Yep, the characteristics of the quake were different.

The movement occurred on shallow reverse (compression) faults. Shallow earthquakes cause more damage than because more energy is released closer to the surface and so stronger shaking occurs. But if the fault had been in the sea, as you noted, the up (or down) movement of the sea floor would have displaced water, which would have been very likely to generate a significant tsunami.

Of note, the official magnitude was determined by the Moment Magnitude scale, not the Richter scale. The Moment Magnitude scale uses additional variables to calculate the energy released using seismic moment, which combines the seismic energy with the offset on the fault and the rigidity of the rock. So the measurement of this particular quake was 7.4 Mw (in U.S. measurement).

https://earthquake.usgs.gov/earthquakes/eventpage/us6000m0xl/technical
 
Sharon Hill said:
Of note, the official magnitude was determined by the Moment Magnitude scale, not the Richter scale.
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Oh, I've never heard of that one. It's difficult to keep up with all the different measurements.
 
Blimey! Has this become an earthquake 'season'?
I mean, we all recall the 2004 Boxing Day Tsunami? The one that triggered the Fukushima event was in March 2011, true. But now we have a major event on New Years Day. :oops:
 
Stormkhan said:
Blimey! Has this become an earthquake 'season'?
I mean, we all recall the 2004 Boxing Day Tsunami? The one that triggered the Fukushima event was in March 2011, true. But now we have a major event on New Years Day. :oops:
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Well, there is a 1 in 12 chance a big quake will occur in any given month. So...
 
This ancient tsunami occurred but was it responsible for a concurrent population decline in Brirain?

About 8,200 years ago, an underwater landslide known as the Storegga slide near Norway triggered a tsunami that engulfed parts of northern Europe.

Around the same time, there was a massive dip in Britain's population. Researchers at the University of York and the University of Leeds looked at whether the disaster contributed to the population decline, or if other factors were at play.

"The suggested population decline occurred immediately after the Storegga tsunami occurred," Patrick Sharrocks, the lead author on the paper detailing the research, told Business Insider via email. "However, a cold period coincided with the tsunami so it was unclear which event had a greater impact."

The researchers built computer simulations of how far the tsunami's waves could have reached inland. Based on their results, the researchers concluded that the tsunami could have wiped out a significant portion of the population at Howick, Northumberland in northern England. They recently published their findings in the peer-reviewed Journal of Quaternary Science.

When the landslides triggered the massive waves, they had widespread impacts. Evidence of the Storegga tsunami has been found in Norway, England, Denmark, Greenland, and Scotland, including the Shetland Islands. Around the mainland of the UK, waves may have reached 10 to 20 feet. Off the coast of Scotland, the Shetland Islands' narrow valleys may have magnified the effects, causing waves of over 65 feet to flood the land.

There aren't written records of the disaster. Instead, the story is in the sediment deposits from lakes, lagoons, and other bodies of water that formed during the tsunami. The wave eroded sediment on land but also brought in more from the sea. While these layers are distinctive, they often erode with time and human activity. However, they can give scientists clues about how far inland a wave traveled and how often similar events occurred. ...

https://www.sciencealert.com/a-massive-tsunami-could-have-wiped-out-populations-in-stone-age-britain
 

Mystery tremors caused by massive nine-day tsunami​

A massive landslide in a Greenland fjord triggered a wave that “shook the Earth” for nine days.

The seismic signal last September was picked up by sensors all over the world, leading scientists to investigate where it had come from.

he landslide - a mountainside of rock that collapsed and carried glacial ice with it - triggered a 200m wave.

That wave was then “trapped” in the narrow fjord - moving back and forth for nine days, generating the vibrations.
“When colleagues first spotted this signal last year, it looked nothing like an earthquake. We called it an ‘unidentified seismic object’,” recalled Dr Stephen Hicks from UCL, one of the scientists involved.

“It kept appearing - every 90 seconds for nine days.”

A group of curious scientists started to discuss the baffling signal on an online chat platform.

“At the same time, colleagues from Denmark, who do a lot of fieldwork in Greenland, received reports of a tsunami that happened in a remote fjord,” explained Dr Hicks. “So then we joined forces.”

The team used the seismic data to pin down the location of the signal’s source to Dickson Fjord in East Greenland. They then gathered other clues, including satellite imagery and photographs of the fjord that were taken by the Danish Navy just before the signal appeared.

The researchers eventually worked out that 25 million cubic metres of rock - a volume equivalent of 25 Empire State Buildings - slammed into the water, causing a 200m-high “mega-tsunami”.
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650-foot tsunami in Greenland fjord made waves that lasted 9 days, scientists find​

Last September, seismologists around the world detected vibrations unlike any they’d picked up before.

A monotonous hum seemed to be emanating from Greenland. It would last for nine days.

“This very, very weird signal showed up that I’d never seen before at some of our stations in the North,” said Carl Ebeling, a seismologist with the University of California, San Diego’s Scripps Institution of Oceanography.

240910-greenland-satellite-fjord-view-ac-750p-b85255.jpg


Soon after the vibrations began, a cruise ship sailing near fjords in Greenland noticed that on the remote Ella Island, a key landmark — a base used for scientific research and by the Danish military for sled dog patrols — had been destroyed.

The events drew an international group of seismologists, the Danish military and oceanographers into the mystery: What had struck the island, and where did it come from?

On Thursday, researchers released their conclusions in the journal Science. The island had been hit by one of the biggest tsunamis ever recorded, they said, with waves that left a watermark about 650 feet high.

The initial trigger came when warming temperatures caused the tongue of a thinning glacier to collapse, the researchers found. That destabilized a steep mountainside, sending a rock and ice avalanche crashing into Greenland’s deep Dickson Fjord. That displaced a massive volume of water, so a towering wave traveled across the narrow fjord, which is about 1.5 miles wide.

The tsunami waves — some at least as tall as the Statue of Liberty — ran up the steep rock walls lining the fjord. Because the landslide struck the waterway at a nearly 90-degree angle, waves bounced back and forth across it for nine days — a phenomenon scientists call a seiche.

“Just a couple of days before the event, cruise ships were there and they were on the beach,” Svennevig said. “It was really, really lucky that no one was there when it happened.”

https://www.nbcnews.com/science/rcna170322

maximus otter
 
Quakes offshore northern California today caused officials to issue a tsunami warning for a huge swath of Calif, Oregon, and Alaska and Hawaii. But a wave did not materialize. It seemed that people in the San Fran bay area headed the warnings but many went toward the shore to gawk. I guess you will never stop that from happening.
 
Sharon Hill said:
It seemed that people in the San Fran bay area headed the warnings but many went toward the shore to gawk. I guess you will never stop that from happening.
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why try to stop natural selection? Except that they would take some non-coms with them I suppose.
 
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