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An ancient underwater vent riding a sinking tectonic home off the coast of Japan may have unleashed several unexplained major temblor — by grind against another tectonic plate above it , a novel subject area finds .
The extinct underwater volcano , bang as Daiichi - Kashima seamount , sits on the Pacific tectonic plate rough 25 miles ( 40 kilometer ) off Japan ’s east coast . There , three tectonic plates intersect — with the Pacific shell to the east and the Filipino plate to the Confederacy both steal beneath the Okhotsk plateful to the Second Earl of Guilford . The seamount sit on a discussion section of the plate that began descending into Earth ’s mantle between 150,000 and 250,000 years ago , study co - authorEunseo Choi , an associate professor at the University of Memphis ' Center for Earthquake Research and Information , secernate Live Science .
The Minami Kasuga 2 submarine volcano, part of the Izu-Bonin-Mariana Arc stretching across the Pacific from Japan to Guam, is one of thousands of seamounts scattered across the seafloor.
But the seamount is still tightlipped enough to the surface to trigger earthquake , as it presently sits less than 31 miles ( 50 km ) deep , said lead authorSungho Lee , a postdoctoral researcher at the University of Memphis . While the majority of the seismic activity around the seamount manifest as low tremors , there have been several earthquake betweenmagnitudes 7 and 7.8 — in 1982 ( 7 ) , 2008 ( 7 ) and 2011 ( 7.8 ) — that previous research has failed to excuse , Lee tell Live Science .
When a tectonic plate slips , or subducts , beneath another home base , the seamounts pelt across its surface scraping against the bottom of the overriding plate . A2008 studysuggested this detrition was too weak to trigger seism , make only very modest tremors , Lee say .
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But newer data indicate the opposite , he enounce . Seismic data gathered at the bottom of the ocean in Japan indicates seamounts encounter huge underground as they turn on along on a subducting home base and sometimes become stuck . " The seamount itself is almost stationary , because it has very secure detrition , " Lee enunciate .
As the seamount grind into the overriding plate , stress accumulates on its lead edge . The realm around the seamount becomes locked and labour to a stop in what the authors term a " hang up up " event , while the rest of the subducting plate continues its creeping line of descent into Earth ’s mantle .
" accent increase at the edge of the seamount and after some time , the stress propagates and transmigrate inward , " Lee said . This buildup can not continue infinitely , he add , and the stress is eventually released when the seamount dead release itself from the overrule plate and jerks frontwards .
The overriding plate jolts in the opposite counseling , triggering a fresh kind of earthquake that Lee and his colleagues call a hang - up earthquake in their report , published Nov. 20 in theJournal of Geophysical Research : strong Earth .
Hang - up quake , which can reach magnitude much greater than 7 , may have unleashed tsunamis in the past , Lee said . Sediment deposits along Japan ’s east seacoast argue vast waves battered the coastline in 1677 , after an earthquake shook an domain overlap with the Daiichi - Kashima seamount .
" The severance of the subducted seamount thus supply the most plausible source for these slap-up tsunami earthquakes , " the researcher write in the study .
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Daiichi - Kashima is a " choice representative " of a subducting seamount that cause enormous friction , Lee said . The researchers pick out this region because of the teemingness of useable data , but their results belike also apply to other region of the world , he added .
It ’s unreadable whether Daiichi - Kashima could trigger an quake anytime shortly . " order of magnitude 7 earthquakes have been occur quite regularly , " Choi say . Records show the surface area around the seamount has get expectant earthquakes every 20 years or so since 1920 . This trend changed in 2011 , when a order of magnitude 7.8 earthquake shook Japan just three years after a magnitude 8 earthquake in 2008 .
" Another one was expected soon , but theTōhoku earthquakedisrupted the tenseness field of honor , search like , so maybe the clock has been reset , " Choi said .
As for other seamount sit off Japan ’s east coast , it will take them at least a million years to reach the subduction zona and another 2 million years to set off earthquakes , Choi say .
