An underwater fault line along the US West Coast could trigger a megaquake that would be more devastating than California's 'Big One,' a new study suggests.
Using underwater mapping techniques, scientists have mapped theCascadia Subduction Zone- a 600-mile fault line extending from southernCanada to northern California-in never before seen detail.
It has revealed that the fault splits into four segments instead of being one continuous strip like most fault lines.The discovery could prove more catastrophic because the tectonic plates can slide under each other, creating more pressure and more severe earthquakes.
The researchers concluded the Cascadia Subduction Zone has the potential to unleash a nine-plus magnitude quake.
The Cascadia Subduction Zone extends along a 600-mile strip of the Pacific Ocean off the coast of southern Canada , Washington, Oregon and northern California.If it erupted, it could cause a magnitude-9 earthquake to strike the region. The darker areas mark the region that would receive the most damage, extending inland where the devastation would be more moderate
If the fault ruptured, it could last roughly five minutes and generate tsunamis reaching 100 feet tall, damage more than half a million buildings and kill countless people in its wake. Pictured: 9.0 earthquake devastated Japan in 2011
California's San Andreas is poised for an up to 8.3-magnitude quake, for comparison.
If anearthquakeof over 9 magnitude struck the West Coast US it could generate tsunamis reaching 100 feet high or more, kill more than 10,000 people and cause over $80 billion in damages in just Oregon and Washington alone.
Disaster emergency plans in Oregon and Washington warn that in the aftermath of a quake that big, they could face a wave of long-term deaths due to disease from exposure to dead bodies, animal carcasses, contaminated water and Hazmat spills from commercial, industrial and household sources.
A similar fault zone off the coast ofJapanerupted in 2011, creating a magnitude 9 quake that causeda devastating tsunami to strike the country, killing nearly 20,000 people.
Now scientists are worried that a similar calamity could impact the US in the coming years, reporting that quakes caused by Cascadia occur roughly every 500 years, with the last one taking place in 1700.
'The recurrent interval for this subduction zone for big events is on the order of 500 years,' Wang said.
'It's hard to know exactly when it will happen, but certainly, if you compare this to other subduction zones, it is quite late.'
Cascadia's four segments make it more dangerous than other major fault lines because they have different rock and sediment, with the most concerning section extending along northern Oregon, into Washington and southern British Columbia.
'It requires a lot more study, but for places like Tacoma and Seattle, it could mean the difference between alarming and catastrophic,' said study co-author Harold Tobin, a geophysicist at the University of Washington.
This section of Cascadia is flatter and smoother than the other three sections, meaning it could cause the largest earthquakes, extending further into the US and impacting all of Washington's coastal communities.
A magnitude nine earthquake in the northwest US could destroy half a million homes and cause the deaths of countless people. Pictured: Aftermath of the 9.0 quake that struck Japan in 2011
'We have the potential for earthquakes and tsunamis as large as the biggest ones we've experienced on the planet,' Tobin told NBC News.
'Cascadia seems capable of generating a magnitude nine or a little smaller or a little bigger.'
Suzanne Carbotte, the study's lead author and marine geophysicist at Lamont-Doherty Earth Observatory, said this is the first clear picture of the Cascadia zone, adding that all emergency response models are based on 'old, low-quality 1980s-era data.'
The researchers hope their findings help states in the impact zone prepare for a worst-case scenario emergency response and evacuation if the Cascadia Subduction Zone ruptures.
If an earthquake of this magnitude struck, it could generate tsunamis reaching 100 feet high or more, effectively altering the region. A similar fault zone off the coast of Japan caused the devastating tsunami to strike the country in 2011, (pictured) killing nearly 20,000 people.
Neither Oregon nor Washington state is sufficiently prepared for this type of disaster because of the limited information in the 1980s Cascadia model, according to the researchers.
However, they said new preparedness assessments could be published as early as next year.
The subduction zone map was created using active source seismic imaging - which emits sounds down to the ocean floor and processes the echoes - that gives a sharper insight into how it can impact the surrounding area.
Researchers at the Columbia Climate School attached a streamer - a nine-mile-long cable - to the back of the boat which used 1,200 hydrophones that captured the echoes to update their ocean acoustic tomography models that provide images of the fault.
Hydrophones measure the amount of time it takes for sound to bounce off the structures on the ocean's floor and reach the surface, allowing them to detect the differences in the elevation of rocks that signifyrecently active fault lines.
'The accuracy and this resolution is truly unprecedented. And it's an amazing data set,' Kelin Wang, a research scientist at the Geological Survey of Canada who was not involved in the study, told NBC News.
'It just allows us to do a better job to assess the risk and have information for the building codes and zoning.'
