The long-term monster earthquake in Oregon and Washington near California could cause some coastal areas to sink more than 6 feet, greatly increasing the risk of flooding and fundamentally reshaping the area with little warning.
These are the findings of a new study that examines the effects of a large-scale earthquake in the Cascadia subduction zone, which runs from Northern California to Vancouver Island in Canada.
The study, published Monday in the Journal of the National Academy of Sciences, concluded that in earthquake scenarios, the highest level or landing areas at risk of flooding would expand by 116 square miles, 2.5 times that of San Francisco.
The study’s authors write that this situation will not only be “flood exposure to residents, structures and roads”, but officials need to compete with “eclectic roads and bridges” and lifelong and infrastructure that are flooded more frequently or permanently in the future.
In other words, a strong earthquake in this area will risk “significantly changing coastlines, with far-reaching and lasting impacts on coastal populations, infrastructure and ecosystems.” Unlike the more gradually driven relative sea level rise in climate change, the rise caused by the major earthquake “will happen within minutes and there is no time to adapt or mitigate.”
According to the U.S. Geological Survey, the village has sunk and must be abandoned, and the last giant giant in the Cascadia subduction zone is a level 900 monster.
From California's North Coast to Washington State, the next huge earthquake (magnitude 8 or higher) could cause land to sink 1.6 to 6.6 feet, the same range as during the 1700 earthquake, the scientists said.
Currently, more than 8,000 people live in the flood level area along the estuary of the estuary of the Cascadia coastal area. However, if there is a high settlement level after an earthquake, the number will almost triple, exceeding 22,000, the study calculated.
The resulting geological flood level will be threatened by nearly 36,000 structures, an increase of 13,000 from the current figure.
On the new flood level, another 777-mile road would almost triple the high risk to 1,212 miles of road.
According to the Federal Emergency Management Agency, flood levels are defined as areas with at least 1% flooding each year, which is considered "high risk." These areas have flooded at least four points in mortgages in at least 30 years. Flood insurance must be purchased by households and business owners in high-risk areas and mortgaged from federally regulated or insurance lenders.
The study said radiocarbon years show that over 11 earthquakes have occurred on the coasts of northern California, Oregon and Washington over the past 6,000 to 7,000 years, frequently occurring every 200 to 800 years.
"The gradual climate-driven sea level rise is not the only threat of submersion," the study said. "The next huge (Cascadia subduction zone) earthquake could produce coastal settlements of more than 3 feet of relative sea level rise, earlier than others expected.
In discussing the future of the Big Quarks in the Cascadia subduction zone, “We often hear about tsunamis and shaking. But, as the earthquake has been happening for decades – for decades – after flooding, it will continue – completely transforming flooding,” Tina Dura, assistant professor of technology in Virginia, has been introduced in Virginia among the leading authors of the study.
An estimate published by FEMA is that a magnitude 9 earthquake along the 800-mile fault zone will kill 5,800 people. The resulting tsunami will kill 8,000 people, which could rise to 80 feet and provide warnings for coastal areas that are only 10 minutes away. Total economic losses could reach $134 billion.
This map shows the location of the Cascadia subduction zone.
(FEMA)
In the giant focal focal 1700 of Cascadia, oral history describes a tsunami of up to 50 feet high, wiping the coastal villages. According to the U.S. Geological Survey, only one out of more than 600 people survived in an Anacla, now known as Vancouver Island.
The tsunami is so powerful that it uproots the trees. When it finally retreated, it found the treetops scattered by garbage and the victim's limbs. USGS said the "ghost forest" of rotten trees found in tidal swamps and river estuaries proved that it sank and flooded the trees during the earthquake.
The results of the latest research should be a call to residents and government officials, considering Quare's response, scientists said. "We have some parts of our area where conventional flooding during unusually high King tides," Dura said, "and places like this may be the hot spots of flooding immediately after the giant earth." ”
Other factors that officials should consider are whether critical infrastructure (such as airports) will fall into the flood level of geological expansion.
Dura said authorities may also want to consider avoiding construction infrastructure in areas “we have proven that they may become flood level lands”, such as schools, fire departments and wastewater treatment plants. ”
This study includes:
Traditionally, scientists and government officials have focused on climate change-driven sea level rise to calculate projected increased risk of coastal flooding. But this study believes that ignoring the role of major earthquakes will be short-sighted.
"After recent historical earthquakes, seismic-driven coastal settlement has had a serious impact on communities, resulting in permanent land loss, infrastructure loss and forced relocation," the study said.
An example is the 2011 magnitude 9.1 earthquake on the east coast of Japan, which caused some land to sink 3 feet. According to news reports, in an area of underground towns, sinking land forces people to fight regularly.
Another magnitude 9.1 earthquake hit near Sumatra, Indonesia, in 2004, caused land to settle up to 3 feet. Since then, areas used for aquaculture have suffered chronic tidal flooding, resulting in excessive desalination and land has been lost, the study said.
The 1964 Alaska earthquake caused coastal areas to sink more than 6 feet, the study said, “rendering roads, docks and waterfronts are uninhabitable, and in some cases it is necessary to relocate communities to higher ground above high levels or to raise land facilities and air runways.” In some places, settlement is even more severe.
Before the 1964 magnitude 9.2 earthquake in Alaska, the sidewalk from the shop on the right of Anchorage was flat with the sidewalk on the left.
In 1960, a magnitude 9.5 earthquake in Chile caused up to 8 feet of coastal settlement, "permanently flooded coastal pine forests and farms, transforming them into intertidal swamps, flooding coastal towns and forcing residents to abandon their homes," the study said.
In addition to the dura, the study has 19 other co-authors, including Singhofen Halff Associates in Orlando, Florida. University of Oregon; Rowan University; University of North Carolina; University of Durham; USGS; Cal Poly Humboldt; Department of Geology and Mineral Industry of Oregon; University of Hong Kong; and South South Technical University in Singapore.