An earthquake of long -term monsters in the coast of California, Oregon and Washington could cause flow of certain coastal areas by more than 6 feet, considerably increasing the risk of radical flood and remodeling of the region with little or no warning.
It was the results of a new study that examined the repercussions of a solid earthquake in the Subduction area of Cascadia, which extends from northern California to Canada Island in Vancouver.
Study, Published Monday in the Revue Proceedings of the National Academy of Sciences, concluded that in an earthquake scenario with the highest level of subsidence or an earth well, the zone at risk of flood would extend from 116 square miles, a band that is 2½ times the size of San Francisco.
Such a scenario would be more than “the exposure to the floods of residents, structures and roads”, and civil servants should face a future of “compromise roads and bridges”, as well as lines of life and infrastructure which are either more frequently flooded or permanent, wrote the authors of the study.
In other words, a powerful earthquake in this area would risk “considerably modifying shores and provoking deep and lasting impacts on coastal populations, infrastructure and ecosystems,” said the study. Unlike the relative elevation of the sea level which is more gradually caused by climate change, an increase resulting from a major earthquake “will occur in a few minutes, leaving no time for adaptation or attenuation”.
The last mega-biker in the Cascadia subduction area, a magnitude 9 monster, occurred in 1700. Based on archaeological evidence, the villages have flowed and had to be abandoned, according to the US Geological Survey.
From the north coast of California to Washington's state, scientists say that the next major earthquake – magnitude 8 or more – could cause a flow of the earth from 1.6 to 6.6 feet, the same beach observed during the earthquake of 1700.
Currently, more than 8,000 people live in flood plain areas along the estuaries in the Coastal region of Cascadia. But if there is a high level of subsidence after an earthquake, this figure would be almost triple to more than 22,000, the study calculates.
Nearly 36,000 structures would be threatened by the flood plain influenced by the resulting earthquake, an increase of 168% compared to the current figure of around 13,000.
And 777 additional road miles would be in the new floodplane plain, tripling almost the total at risk at 1,212 miles of road.
The flood plain is defined as areas that have at least 1% of flooding each year, which is considered a “high risk”, according to the Federal Emergency Management Agency. These are areas that have at least 1 in 4 flooding in a mortgage of 30 years. Flood insurance must be purchased by owners of houses and businesses in high -risk areas with mortgages from regulated lenders or provided by the federal government.
Dating to the radiocarbon suggests that there have been more than 11 large earthquakes off the shore of the north coast of California, Oregon and Washington State in the last 6,000 to 7,000 years – recurrent every 200 to 800 years, the study said.
“The gradual increase in climate sea level is not the only threat of flood,” said the study. “The coastal subsidence of the next large (area of subduction of the cascadia) can produce” more than 3 feet of the sudden climb of the relative sea than expected.
When you discuss a future Mega-Biké on the Cascadia subduction area, “we often hear about tsunami and tremors. But there is the subsidence that will persist – for decades at centuries – after the deputy professor of Geosciences by Virginia Tech and the main author of the study, said in an interview.
A published estimate by fema is that an earthquake of magnitude 9 over the entire length of the 800 -mile flaw zone would leave 5,800 dead from the earthquake alone. 8,000 others would die from the resulting tsunami which could go up to 80 feet and offer coastal areas for a few 10 minutes of warning. Total economic losses could reach $ 134 billion.
This card shows the location of the Cascadia subduction area.
(Fema)
In the 1700 Cascadia Megaquake, oral stories describe tsunamis more than 50 feet high, destroying the coastal villages. In Anacla, a village on what is now called the island of Vancouver, only once on more than 600 people, according to the US Geological Survey.
The tsunami was so strong that it uprooted the trees. When he finally fell, peaks to summits were found dotted with waste and members of the victims. The “ghost forests” of trees resistant to rot found in the tidal marshes and the region's estuaries prove that the earth flowed during the earthquake and drowned the trees, said the USGS.
The results of the latest study should be an alarm signal for residents and government representatives considering a post-Shake response, scientists said. There are already parts of the American Route 101 who flood regularly for exceptionally high King Tides, Dura said, “And places like that could be a little hot spots to see floods immediately after sagging” after a mega-terre.
Other factors should consider themselves as if critical infrastructure, such as airports, are located in the flood plain exposed to the earthquake, according to scientists.
Authorities may also consider avoiding construction infrastructure such as schools, fire station and wastewater treatment factories in areas “we have shown should become in the flood plain,” said Dura.
Notable areas at risk of pouring land following a megaquia along the Cascadia subduction zone, according to the study, include:
- The Humboldt Bay region in California, including the area around Eureka and Arcata.
- In Oregon, Waldport and Bayshore along the Bay of Alsea; Newport and South Beach along Yaquina Bay; and Gearhart and Seaside along the Necanicum river.
- In Washington, the Willapa Bay region, including Long Beach, Ocean Park, Tokeland and Raymond communities; and the Grays Harbor region, including Ocean Shores, Westport and Aberdeen.
Traditionally, government scientists and representatives have concentrated on Elevation from sea level to climate change To calculate the increased risk projected of coastal flood. But the study argues that the negligence of the role of major earthquakes is short.
“The coastal drawback focused on earthquakes after recent historical earthquakes has had serious consequences for communities, resulting in permanent loss of land, infrastructure damage and forced reinstallation,” said the study.
An example was the Magnitude 9.1 Trewkee Off the east coast of Japan in 2011, which caused land to 3 feet. In an area of the city of Ishinomaki, the flowing earth forced people to face floodaccording to reports.
Another earthquake of magnitude 9.1 who struck near SumatraIndonesia, in 2004, caused land of up to 3 feet. The areas used for aquaculture have since undergone chronic tide floods, leading to overestimation and land has been lost, the study said.
The earthquake of 9.2 in Alaska in 1964 to flow the earth More than 6 feet along the coast, “making the roads, the quays and the areas at the edge of the water uninhabitable, in some cases, requiring the relocation of communities for higher purposes or to raise installations by the water and pistols above the high tide,” said the study. In some places, sagging was even more serious.
Before the earthquake of magnitude 9.2 of 1964 in Alaska, the sidewalk in front of the stores on the right side of this anchorage photo was level with those on the left.
And an earthquake of magnitude 9.5 in Chile in 1960 caused up to 8 coastal feet, “submerging definitively forests and coastal farms and converting them into intertidal marshes, and flooding coastal cities and forcing residents to abandon houses,” said the study.
In addition to Dura, there are 19 other co-authors under study, with affiliations including Singhofen Halff Associates d'Orlando, Florida; The University of Oregon; Rowan University; the University of North Carolina; University of Durham; USG; Cal Poly Humboldt; The Department of Geology and Mineral Industries of Oregon; The University of Hong Kong; and Nanyang Technological University in Singapore.
