When the earthquake teared along the faults along the Cascadia subduction zone, most of the west coast of the United States may shake violently for five minutes, with the tsunami as high as 100 feet, possibly on the shore barrel. But this is just the beginning of the expected horror.

New research shows that even coastal towns in northern Northern California are under the fierce attack of such earthquakes, floods can perpetuate many of these vulnerable communities. This is because the entire coastal coastline is expected to drop as much as 6½ feet when the earthquake hits, according to new research published Monday in the Proceedings of the National Academy of Sciences.

The researchers analyzed earthquake and flood models to produce some of the most detailed estimates to understand how the Cascadia earthquake will fall or fade off the coastal coastline, finding that it could affect more than twice the current risk of people, structures and roads. Over time, as climate change intensifies, this impact will also worsen over time.

"This less talk of danger will continue for decades or centuries after the earthquake," said Tina Dura, lead author of the study. "The tsunami will come in and wash away, which will have a big impact, don't get me wrong, but the lasting change in flood frequency...has to be dealt with."

Dura said geological fossil evidence suggests that the previous Cascadia earthquake immediately dropped the land, turning the dry ground into tidal mud at the estuary along the Pacific Northwest. “This will happen again, we have established many areas,” said Dura, an assistant professor at Virginia University of Technology. “That’s how we have the port there…this is where we build towns and all the areas will drop to over one metre, up to two metres.”

The Cascadia subduction zone fault follows the offshore from Northern California to Vancouver Island along the west coast of North America, which is an imminent threat. The fault has the ability to produce an amplitude of 9.0 earthquake and on average every 450-500 years there is at least one large temblor there. The last of these major earthquakes occurred in 1700.

National earthquake hazard models show that 15% of the amplitude 8.0 earthquakes or stronger earthquakes will break along the edge of the region over the next 50 years.

Experts say that when the fault tear it will cause the worst natural disaster in U.S. history. A state and federal planning activity for the 2022 Cascadia earthquake predicts about 14,000 deaths, more than 100,000 injured, and about 620,000 buildings collapsed in the Pacific Northwest, including 100 hospitals and 2,000 schools.

The new study suggests that coastal planners must consider not only the threat of strong shaking and tsunami waves, but also the long-term reshaping and rapid sinking of the coastline itself.

“There is flooding itself, and then there is basically a permanent change in the land level of the coast, which has a big impact on what these communities have to plan for,” said the director of the Pacific Northwest Earthquake Network, a professor at the University of Washington, who is not involved in the new research. "Where are you going to put the school or hospital? Where are you going to build a transportation network? I think the vision is important."

After the earthquake, Dura's research showed that most towns along the Pacific Northwest coastline, such as the Oregon seaside. Westport, Washington; Aberdeen, Washington is expected to flood at least every 100 years, if not more frequently.

The study also points out that as climate change intensifies, sea level rise is accelerating, and the impact of post-Earth flooding may worsen.

According to the National Oceanic and Atmospheric Administration, global average sea levels have risen by about 8 to 9 inches since 1880. Due to global warming, sea level rise is expected to accelerate significantly over the next few decades, with NOAAs on average predicting to average 10 to 12 inches in the Middle Ages. Where you live can determine the occurrence of sea level and how it affects the shoreline.

While land in some parts of the United States is slowly sinking in a process called settlement, parts of the Pacific Northwest have been rising due to the rise of the continent. Rising land levels have offset some sea level rise to date.

Uplift is the result of pressure accumulated in the tectonic plates that make up the coast of the Cascadia subduction zone. On the subduction zone, the Juan de Fuca plate was forced under the North American continental plate. This causes the North American plate to bend slightly upward, thereby increasing the land level.

Currently, the failure of the subduction zone is quiet and pressure is established. When the fault breaks, the bow of the plate will release and cause rapid settlement at the land level, essentially eliminating the speed of centuries.

"This happens within minutes and can be done in the order of meters," Dura said. "This land continues, like I said, it's probably decades and centuries. So now any area of ​​the floodplain is in it."