The Cascadia fault line is the focus of the new study conducted by Proceedings of the National Academy of Sciences. It breaks down the flooding potential a 9.0 earthquake could bring to the Pacific Northwest and the Northern California coastline.
It's a fault about 700 miles long, running from Northern California all the way up to Vancouver, British Columbia, capable of producing a massive quake - which was last seen in 1700.
While the study could look alarming, it's a possibility that has actually been known for a few decades. But according to seismologist Dr. Lucy Jones, the bigger concern is actually in Southern California.
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Jones told Eyewitness News while we could still see damage for coastal areas, the fault line is offshore, so the heaviest shaking would be underwater.
"So, basically all of the coast of Northern California, Oregon and Washington will be like the San Fernando Valley in the Northridge earthquake," Jones said. "We had 10 miles and this is going to be 700 miles or something like that. So it's going to be a much larger area that is hit by the shaking."
The study provides calculations of possible scenarios of where coastal areas could sink by several feet.
"I think the other aspect as sort of the newsworthy thinking about it is what does it mean in the time of sea level rise? And it's another compelling reason to really do something about climate change," Jones said.
But Jones says the possibility of this monster earthquake actually isn't the worst-case scenario.
"The most damaging earthquake I could think about is not even on the San Andreas, it would be a magnitude 7.5 under Los Angeles. Because the thing in the west coast, where we have relatively young rocks, compared to the east coast and they're softer then."
So where exactly are the most concerning areas? Dr. Jones lists the faults capable of a 7-magnitude as the Newport-Inglewood Fault, Hollywood, Santa Monica, Whittier and Puente Hills.
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She says there are about 100 faults under Los Angeles, but the worst model output is the Puente Hills Fault - which runs right under downtown L.A.
"It's bad luck if you happen to hit the century that we have the magnitude 9, but those 7s in Los Angeles are more deadly," she said.