An undersea fault along the US West Coast could trigger a mega-earthquake that would be more devastating than the “Great California Earthquake,” a new study suggests.
Using underwater mapping techniques, scientists have mapped the Cascadia subduction zone, a 600-mile fault line that extends from southern Canada to northern California, in never-before-seen detail.
It has revealed that the fault is divided into four segments rather than being a continuous strip like most faults. The discovery could prove more catastrophic because tectonic plates can slide under each other, creating more pressure and more severe earthquakes.
The researchers concluded that the Cascadia subduction zone has the potential to trigger an earthquake of magnitude greater than nine.
The Cascadia Subduction Zone extends along a 600-mile swath of the Pacific Ocean off the coasts of southern Canada, Washington, Oregon and northern California. If it were to erupt, it could cause a magnitude 9 earthquake in 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 were to rupture, it could last approximately five minutes and generate tsunamis up to 30 meters high, damaging more than half a million buildings and killing countless people in its path. Pictured: A 9.0 magnitude earthquake devastated Japan in 2011
By comparison, San Andreas, California, is primed for a magnitude 8.3 earthquake.
If an earthquake of magnitude greater than 9 were to hit the west coast of the United States, it could generate tsunamis that would reach 100 feet or more in height, kill more than 10,000 people, and cause more than $80 billion in damage in Oregon and Washington alone.
Emergency disaster plans in Oregon and Washington warn that after an earthquake of that magnitude, they could face a wave of long-term deaths due to illnesses resulting from exposure to dead bodies, animal carcasses, contaminated water and material spills. hazardous substances from commercial, industrial and domestic sources.
A similar fault zone off the coast of Japan erupted in 2011, creating a magnitude 9 earthquake that triggered a devastating tsunami that hit the country and killed nearly 20,000 people.
Now scientists are worried that a similar calamity could hit the US in the coming years, reporting that earthquakes caused by Cascadia occur approximately every 500 years, with the last one taking place in 1700.
“The recurring interval of this subduction zone for large 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’s pretty late.”
Cascadia’s four segments make it more dangerous than other major faults because they have different rocks and sediments, with the most concerning section stretching across northern Oregon to 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 gentler than the other three sections, meaning it could cause the largest earthquakes, spreading further into the US and impacting all of Washington’s coastal communities.
A magnitude nine earthquake in the northwest United States could destroy half a million homes and kill countless people. Pictured: Aftermath of the 9.0 earthquake that hit Japan in 2011
“We have the potential for earthquakes and tsunamis as large as the largest we’ve experienced on the planet,” Tobin told NBC News.
“Cascadia appears capable of generating magnitude nine or a little smaller or a little larger.”
Suzanne Carbotte, lead author of the study and a marine geophysicist at Lamont-Doherty Earth Observatory, said this is the first clear picture of the Cascadia area, adding that all emergency response models are based on “old, low-level data.” quality from the 1980s.
The researchers hope their findings will help states in the impact zone prepare for worst-case emergency response and evacuation if the Cascadia Subduction Zone ruptures.
If an earthquake of this magnitude were to occur, it could generate tsunamis that would reach 100 feet high or more, effectively disrupting the region. A similar fault zone off the coast of Japan caused the devastating tsunami that hit the country in 2011, killing nearly 20,000 people (pictured).
According to researchers, neither Oregon nor Washington state are sufficiently prepared for this type of disaster due to limited information in the Cascadia model from the 1980s.
However, they said new readiness assessments could be released next year.
The subduction zone map was created using active source seismic imaging, which emits sounds to the ocean floor and processes the echoes, providing a clearer view of how it may affect the surrounding area.
Researchers at the Columbia Climate School placed a streamer (a nine-mile-long cable) at the back of the ship that 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 ocean floor structures and reach the surface, allowing them to detect differences in rock elevation that indicate recently active faults.
‘The precision and this resolution are unprecedented. And it’s an amazing data set,” said Kelin Wang, a research scientist at the Geological Survey of Canada who was not involved in the study. NBC News.
“It just allows us to do a better job of assessing risk and having information for building codes and zoning.”
