Connect with us

Uncategorized

Most landslides in western Oregon are caused by heavy rainfall, not large earthquakes

Published

on


Coastal Oregon Mountain Range extends from around Newport, Oregon, south to Port Orford. Located near the Cascadia Subduction Zone, the low mountain range is a sea fault that can cause earthquakes of magnitude 9. Credit: LaHusen et al / Science Advances

Researchers at the University of Washington, Portland State University and the University of Oregon have shown that deep landslides in the Oregon Coast Chain are mostly caused by precipitation, not large marine earthquakes.

An open access paper was published Sept.16 in Science Advances.

“Geomorphologists have long recognized the importance of precipitation in triggering landslides, and our study simply leads home how important it is,” said first author Shawn Lahussen, who conducted the work as part of his PhD at the University of Wisconsin. “Our results show that more frequent and localized landslides caused by precipitation are just as important as the less frequent but far-reaching Cascadia subduction zone earthquakes.”

Heavy rains are known to cause landslides that can be devastating and deadly. A less frequent cause of a landslide may be the rupture of a geological fault off the coast of Washington and Oregon known as the Cascadia Subduction Zone – adding to a long list of concerns after a major earthquake. The risk of landslides of all kinds increases if human development or forest fires remove trees and remove roots that stabilize soil.

However, recent research in Nepal and Japan indicates that marine earthquakes may not cause as many landslides as previously thought. The new study found a similar situation in the Pacific Northwest.

“We’re not suggesting that the landscapes had no response to these magnitude 9 earthquakes,” said senior author Alison Duvall, “but that deep landslide deposits and scars on the slopes of the Oregon Coast Range today are mainly caused by precipitation events.” , Associate Professor at the University of Washington in Earth and Space Sciences. “We conclude that previous earthquakes in the Cascadia Subduction Zone did not cause more than a few hundred deep landslides during the events of the Great Earthquake.”

Researchers used high-resolution aerial laser maps of the Oregon coast to examine 1,000 years of landslides. And they found that landslides tend to occur in places with heavy rain. But surprisingly, there was no detectable change in the number of deep landslides at the time of the Great Earthquake that rocked the Pacific Northwest in 1700, or of two previous marine earthquakes in about 1150 and 1470.

Within the study area, shown on the left, analyzes of the aerial lidar images revealed nearly 10,000 landslides. In the subgroup on the right, landslides of the past 1,000 years are shown in red. Credit: LaHusen et al / Science Advances

Duval and Lahuysen and co-author Adam Booth at Portland State University developed a method for dating landslides while studying the site of a fatal mudslide in March 2014 in Osu, Washington. In that study, they used high-resolution images to display the surface roughness. Over time, the soil settles and erodes the exposed rocks. The surface becomes smoother, so the surface roughness can be used to calculate the lifetime of the landslide.

For the new study, they applied their method to a larger area in the Central Oregon Coast Chain. To study landslide activity related to the Cascadia Subduction Zone, researchers required an area near the Cascadia fracture zone with stable rock type and lidar images available to the public.

“The Central Oregon Coastal Range provides a massive 10,000-square-kilometer natural laboratory for exploring patterns in deep landslide events across space and time,” said Lahussen. “It is a sandstone and a 50 million-year-old silt stone that was deposited in the sea, buried, compressed and then raised to form the mountains that we see today.”

Aerial lidar maps with a resolution of less than 3 feet revealed 9,938 landslides within the study area. Researchers reduced the number of landslides to 2,676 landslides that occurred during the past 1,000 years, and then studied the frequency of landslides during that period.

The researchers warn that the study does not apply to shallow landslides, which often occur during earthquakes but do not leave long-term evidence and cannot be analyzed in this way, or to different soils, and thus not necessarily apply to other soils. Regions. The research did not take into account surface earthquakes caused by surface faults.

But the study supports recent findings in Asia that indicate that marine earthquakes do not cause as many deep landslides as previously thought, and that rainfall may be the largest factor in shaping landscapes over longer periods of time.

“These data reinforce the point that we do not need large earthquakes to cause large and devastating landslides in Washington and Oregon,” Duval said. “Monsoon rains and major rain events are important to focus on in landslide preparedness planning.”

The history of historical activity at the Oso site shows frequent major landslides. More information: “Rainfall causes more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Series, USA” Science Advances (2020). advances.sciencemag.org/lookup….1126 / sciadv.aba6790 provided by the University of Washington

Quote: Most of the landslides in western Oregon have been recovered due to heavy rainfall, not large earthquakes (2020, September 16) on September 16, 2020 from https://phys.org/news/2020-09-landslides-western-oregon- triggered-heavy. programming language

This document is subject to copyright. Notwithstanding any fair treatment for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos



Picture Credit!

ExBUlletin

to request, modification Contact us at Here or [email protected]

Please disable the ad-blocker on this page to see the content

plus