Japan Earthquake Shifted Seafloor by 79 Feet
for National Geographic News, Published May 19, 2011
An acoustic transponder that tracks earthquake movements is installed off Japan in an undated picture.
Japan’s seabed moved by as much as 79 feet (24 meters) during the giant March 11 earthquake—the largest earthquake slip ever recorded, scientists say.
But that doesn’t mean that it’s the largest such shift ever to have been caused by an earthquake, cautioned Chris Goldfinger, director of the Active Tectonics and Seafloor Mapping Laboratory at Oregon State University.
The March earthquake was, however, the first time that scientists have directly measured such a slippage thousands of feet of underwater.
“Any magnitude 9 earthquake will have similar values,” said Goldfinger, who was not part of the study team.
For instance, the 2004 Sumatra earthquake may have moved the seabed by as much as 100 feet (30 meters), he said by email.
(Related: “Japan Earthquake Shortened Days, Increased Earth’s Wobble.”)
GPS Technology Tracks Fault Movements
For several years, a team led by Mariko Sato of the Japan Coast Guard has been monitoring particular spots along the Japanese fault that produced the recent earthquake.
Scientists had placed transponders on the seabed. Using high-precision sonar techniques, the researchers could then record the transponders’ locations from research vessels, whose own locations were carefully tracked by GPS satellites.
(Related: “Earthquake Fault Under Tokyo Closer Than Expected, Study Finds.”)
This two-step technique is necessary, because GPS signals cannot reach the seabed, Sato said by email.
Shortly after the Japan earthquake occurred on March 11, the scientists returned to measure the changes.
“This is the first time a great subduction earthquake has been directly observed in the submarine part of the fault, which is where most of the action takes place,” noted Oregon State’s Goldfinger.
“We normally have to infer slips from onshore GPS,” Goldfinger said. “Being able to measure it directly is very useful. It confirms the ability to model it from shore. It will help quite a lot in refining such models.”
Understanding Future Tsunamis, Earthquakes
Overall, the more we learn about such earthquakes the better, Goldfinger added. Pre-2011 tectonic models, for example, did not predict a big earthquake around the site of the March epicenter near the east coast of Honshu island, Japan. (Read more about earthquake prediction.)
Furthermore, such research is useful in understanding tsunamis, research leader Sato said by email.
“It is important to continue monitoring seafloor movements in order to evaluate the risks of future earthquakes and tsunami.”
http://news.nationalgeographic.com/news/2011/05/110519-japan-earthquake-tsunamis-science/
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Geologist discovered that the sea floor was moving outward from the midoceanic ridges. It seem that sea floor spreading formed a new basaltic oceanic crust forms at a midoceanic ridge. New geographic features can be created through seafloor spreading. Japan’s seabed has moved during the giant earthquake and Scientists had placed transponders on the seabed to check the movement of seabed.
The theories of continental drift and sea floor spreading were supported by reliable scientific data and combined to develop modern day technology. It is important to continue monitoring seafloor movements in order to evaluate the risks of future earthquakes and tsunami.
Thank you Rinpoche for sharing this information.
Whilst earthquakes are still being felt around the world, recordings showed that Japan’s previous giant earthquake shifted the seafloor by 70feet(24meters) seemingly the largest earthquake slip ever recorded. Nevertheless, Chris Goldfinger, director of the active Tectronics and seafloor mapping lab. at oregon state university, cautioned otherwise that “that does”nt mean it the largest such shift ever to have caused by an earthquake”. The march earthquake with an magnitude was however the first time that scientists have directly measured such a slippage thousands of feet deep underwater. Golfinger reiterated that to enable more accurate prediction, it is important to have a continual monitoring of seafloor movements on a wilder scale in the surrounding regional areas to evaluate the rises of future earthquakes and Tsunamis. Japan seems to have a sea of phenomenas, just as after this contravasy, another 5.8 magnitude earthquake was reported to hve hit Tokyo again, causing tremors and fears, though no major damages were emmiently noted.