Seiche - Harmonic Standing Wave (Distinct From Tsunami)

Mighty_Emperor

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I am amused how vague some of these reports are:

Earthquake felt in Oklahoma, too
From Phoenix staff reports

For information on earthquakes: Jim Lawson, chief geophysicist, 366-4152; and Amie Friend, 366-4152; or go to www.okgeosurvey1.gov

The largest earthquake in 50 years that occurred near Northern Sumatra, Indonesia, may have caused water in Oklahoma ponds and lakes to slosh back and forth slowly, officials said Monday.

This motion is called a seiche. It also may have caused some tall buildings in Oklahoma to sway slightly, said Jim Lawson, chief geologist with the Oklahoma Geological Survey.

In the Sooner state, 9,700 miles away, the OGS recorded waves from the quake beginning a 7:13 p.m. Sunday. The largest waves, with 0.12 inch vertical movement in Oklahoma, were recorded at 7:36 p.m.

Last year, an earthquake measuring 8 on the Richter scale in Alaska caused ponds to slosh back and forth, Lawson said.

"Considering that since this is on the other side of the earth, it would be very interesting if the waves were large enough to cause a pond or number of lakes to resonate," he said.

He said someone standing near the shore possibly could have seen the movement in a pond or lake.

Anyone observing a sieche, tall buildings swaying, or other phenomenon in Oklahoma around 7:36 p.m. Sunday, are asked to report it at www.okearthquakes.us/report.html.

The OGS Observatory, near Leonard, west of Muskogee in Tulsa County, is responsible for information and research about Oklahoma's earthquakes.
Source
Link is dead. See Wayback Machine:
https://web.archive.org/web/2005011.../news/stories/20041228/localnews/1795857.html
 

Obake

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Its hard to comprehend, I think, just how much energy is released in an event like the 2011 Tohoku earthquake.

Norway's Weird Waves Traced to Japan Earthquake
LiveScience.com
By Becky Oskin, Staff Writer 1 hour ago Japan

On a calm winter's day in Norway two years ago, the sea suddenly started to boil and rise, sending freak waves rolling onto nearby shores and mystifying residents. Turns out, the massive magnitude-9.0 earthquake that shook Japan in 2011 also triggered these surprise seiche waves, a new study shows.

Seiche (pronounced saysh) waves are standing waves that form in closed or semi-enclosed water basins, such as Norway's narrow, steep-walled fjords. Smaller examples of standing waves include water sloshing in a bathtub from a wriggly child, or in a swimming pool after an earthquake.

The roiling seas surprised and shocked Norwegians when the waves rolled in after 7 a.m. local time on March 11, said lead study author Stein Bondevik, a geologist at Sogn og Fjordane University College in Sogndal, Norway. The waves measured nearly 5 feet (1.5 meters) from trough to crest (their lowest to highest point). No damage was reported, however. "Luckily, they happened at low tide," Bondevik said.

A tsunami expert, Bondevik was called on by local media to explain the source of the surge. Bondevik said he first thought an underwater landslide generated the waves. "They looked like tsunamis," he said. But as the day wore on, more reports of coastal flooding came in from faraway fjords, blowing a hole in his landslide theory.

"Later in the evening I realized there must be a connection with the big earthquake in Japan," Bondevik told LiveScience. "I was so excited I couldn't sleep that night thinking about it." [7 Craziest Ways Japan's Earthquake Affected Earth]

A rare event

Seiches from earthquakes are a common phenomenon — California's swimming pools go berserk after the state's big quakes — but they are rare in Norway. The last earthquake to set off seiches in Norway's fjords was the magnitude-8.6 Assam earthquake in Tibet. The great 1755 Lisbon earthquake in Portugal also unleashed seiches in the fjords.

And not every fjord in Norway started oscillating after the Japan earthquake. Only fjords pointing northeast, toward Japan, were properly aligned, and even then only some of the fjords had the right conditions to launch a seiche, the study found.

Five towns reported seiches the morning of the Japan earthquake. The water in the fjords oscillated for almost three?hours, starting about 30 minutes after the Japan earthquake, the study found. People noticed the waves only where the shores had shallow beaches, such as at river deltas, the researchers said.

The researchers built a computer model of the seiches based on surveillance and camera phone videos, which timed the ebb and flow of the oscillations.

Shimmying the Sognefjorden

The model revealed that S-waves, a type of seismic wave, caused the rare event. S-waves shake back and forth perpendicular to their direction of travel (like waving a rope on the ground) and can pass inside the Earth. In fjords pointed northeast, the S-waves from the Japan earthquake moved the ground back and forth by 0.4 inches (1 centimeter), Bondevik said.

"You can move a lot of water just by pushing one centimeter of ground," Bondevik said.

Earlier studies have suggested seiche waves are triggered by seismic surface waves, which travel more slowly than S-waves and can only pass through Earth's crust. These earthquake waves also contributed to Norway's seiches, but the initial sloshing was sparked by the S-waves, the researchers concluded.

"We have now, because of the film clips, been able to pick out what part of the earthquake shaking triggered the waves in the fjords," Bondevik said. "And to our surprise, it was not the largest or strongest shaking, but the S-waves. They have the correct period that matches up with the fjord's [natural frequency]," he said.

The findings were published July 3 in the journal Geophysical Research Letters.
http://news.yahoo.com/norways-weird-wav ... 59107.html
 
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