Researchers say the Cascadia Subduction Zone generates a major event every 200 to 530 years - and last experienced a quake in the 1700s
FEARS are growing for the “Big One” as experts claim to have found proof a major earthquake AND a massive Tsunami is due to strike California.
The study, led by scientists at the University of Texas, reckon an earthquake is more likely to strike off the coast of Washington and northern Oregon – although a large enough movement would impact the surrounding areas.
Experts say this is because seismic data shows the sediment there is more compact, with a small amount of water sitting in the pore spaces between the grains, leaving the plates more susceptible to a build-up of stress.
These conditions allow the sediment to stick and move together in the event of an earthquake, which means they’re also able to move huge amounts of seawater – resulting in a tsunami.
Shuoshuo Han, who led the study, s
aid: “We observed very compact sediments offshore of Washington and northern Oregon that could support earthquake rupture over a long distance and close to the trench, which increases both earthquake and tsunami hazards.”
The thick sediment layer on the top is scraped off as it moves and piled up on the top plate, forming a thick wedge of material, while the rest of the sediment travels down with the bottom plate.
Nathan Bangs, a senior research scientist at UTIG and study co-author, said: “That combination of both storing more stress and the ability for it to propagate farther is important for both generating large earthquakes and for propagating to very shallow depths.”
The possibility of an earthquake generating in shallow depths is what causes large tsunamis, such as the one that struck Tohoku in Japan in 2011.
Penn State University professor Demian Saffer, who co-wrote the study, said: “The results are consistent with existing constraints on earthquake behaviour, offer an explanation for differences in structural style along the margin, and may provide clues about the propensity for shallow earthquake slip in different regions.”
It comes after a 3.2 magnitude earthquake hit southern California earlier this month.
The epicentre was in Los Angeles – home to Hollywood with a population of 4 million people – which sits on the Ring Of Fire fault line along with other Californian cities like San Francisco.
Experts say California is due another major apocalyptic tremor — which they have already dubbed “The Big One”.
Why are subduction zones prone to large tsunamis?
Subduction zones are especially prone to large tsunamis because as one plate is pushed beneath another, the plates continue to push and lock against each other until stress builds up so much that they slip. Scientists are worried this is currently happening at the Cascadia subduction zone, and any time energy is built up by shifting plates, a large earthquake could occur. Watch this video:
How much time would you have for evacuation?
According to the LA Times, residents would only have about 15 minutes to get to safety. Pretty tight, not? In Grays Harbor County, Wash., they’re beginning to build vertical evacuation centers atop sturdy gymnasiums that will allow teachers and students to quickly evacuate to higher ground in case a massive earthquake pushes a tsunami toward the coast.