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A ruinous earthquake in the Cascadia realm of the Pacific Northwest could lower the ground near the sea-coast by up to 6.6 foot ( 2 metre ) . Combined with rise up sea triggered by mood change , that could make long - term flooding trouble for coastal areas in northern California , Washington and Oregon , a new study find .
Such a quake would triple the amount of land in the 100 - class flood plain in the Pacific Northwest by 2100 , according to the cogitation .
" We talk a lot about the tsunami and about the shaking , but this subsiding could persist for decades to centuries,“Tina Dura , a coastal geologist at Virginia Tech who led the research , told Live Science . " And that ’s going to be something that ’s going to all change these coastal communities . "
Unlike other coastal sphere , the Pacific Northwest has for the most part escaped the impacts of rising sea levels make by mood alteration . That ’s because of the area ’s geology . The coastal Pacific Northwest is asubduction zonewhere oceanictectonic plates(in this case , the Juan de Fuca and Gorda plates ) sink under continental plates ( in this case , the North American Plate ) .
The last metre this Cascadia subduction geographical zone shake off a major earthquake was in 1700 . Since then , the coastline has been rising by 0.04 to 0.12 in ( 1 to 3 millimetre ) a class , slightly outpacing climate - driven ocean - grade emanation in many area . clime change is set to have its day , however , Dura say : By 2030 , the sea level will be rising quicker than Cascadia ’s upthrust .
Geologists have long known that a major Cascadia earthquake could cause the coastline to swing . It ’s bechance in many major subduction - zone temblor before , include the 1960 magnitude9.5 Great Chilean Earthquake , the most herculean earthquake ever recorded . The 2004 Indian Ocean earthquake and tsunami that kill more than 227,000 mass alsocaused the land to slump by as much as 6 feet(1.8 m ) in Sumatra , Indonesia . geologic evidence from the 1700 quake in the Pacific Northwest shows woods becoming mudflats after slumping below sea tier .
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But no one had quantify how this slide down , known as subsidence , would interact with rising ocean levels drive by climate change . Dura and her squad compared the amount of land that would end up in the Federal Emergency Management Agency ( FEMA ) 100 - year floodplain if a magnitude 8 Cascadia seism were to happen today versus in 2100 , when climate - driven ocean - level rise is expected to reach between 1.3 and 2.9 feet ( 0.4 to 0.9 m ) in Cascadia ’s estuary .
They found that in the worst - case scenarios of up to 6.6 feet of subsidence , the area in the 100 - twelvemonth flood plain would increase by 145 straight mile ( 370 straightforward kilometer ) , compared with 115 square mile ( 300 straightforward klick ) if the quake were to shine today . The appellation of a 100 - year flood plain means that an domain has a 1 % opportunity of flooding in a given class .
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The expanding upon of the floodplain would put an additional 17,710 residents in the way of life of flooding . correctly now , 8,120 mass call these floodplains home . The expanded flood plain also holds essential base , such as wastewater treatment plants , electric substations , and municipal airports . Many of these area would be immediately impact by a tsunami from a major Cascadia quake , Dura read , but continued flooding in the consequence could affect evacuation , rescue and rebuilding .
" Could something like melodic line response be interrupt ? " she said . These expanded floodplain maps could help exigency manager and urban center planners set for the worst , she added .
The results were issue April 28 in the journalPNAS .
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