Seismic shock wave pattern may redirect earthquake damage

A fault ruptures in California’s Searles Valley after the 2019 Ridgecrest earthquake. A seismic study led by the University of Texas at Austin finds that seismic shock waves are formed by jagged faults and debris jammed between them. Credit: Ben Brooks/USGS

New research from the University of Texas at Austin could change the way scientists think about potential damage from earthquakes.

The study examined data from one of the densest seismic arrays ever and found that earthquakes emit the strongest seismic shock waves in four opposing directions. The effect, which leaves a four-leaf clover-like pattern, has been known for decades but has not been measured in such vivid detail.

Daniel Trogman, a seismic geophysicist in the Department of Geosciences at UT Jackson’s School of Earth Sciences, said the study looked at only one type of seismic vibration caused by very small earthquakes in northern Oklahoma.

“What’s important about these results is that we’re seeing variation in the motion of the Earth near the source, and that doesn’t account for any kind of risk model,” Trogman said. He added that efforts are already underway to find out how this phenomenon occurs in California’s major fault systems.

The analysis was published in the September issue of Geophysical Research Letters and is based on measurements of twenty small earthquakes recorded by the LArge-n Oklahoma Seismic Survey (LASSO), a group of 1,829 seismic sensors deployed for 28 days in 2016 to monitor a far corner of the state. With an area of ​​15 x 20 miles.

When earthquakes strike, they release a thunderclap of seismic energy at many frequencies, but the actual ground shaking people range from about 1 Hz to 20 Hz. The study found that low-frequency energy – about 1 to 10 Hz – was fired from the fault in four directions, but it was barely recorded outside the four-leaf clover pattern. This is important because buildings are more susceptible to low-frequency waves. No four-leaf clover pattern was found for the high-frequency waves, which were moving with equal force in all directions, like ripples in a pond.

Co-author Victor Tsai, a geophysicist at Brown University, said the reason the Earth vibrates unevenly at different frequencies may have to do with the complex geometry of earthquake faults and the fractured material stacked between them.

A weak earthquake of magnitude 2.03 measured at various seismic frequencies ranging from 2.50 hertz (Hz) to 35 hertz. A study led by the University of Texas at Austin revealed that the earthquake’s low-frequency seismic waves travel in a four-leaf clover pattern. However, above 15 Hz, the pattern collapses and seismic waves travel in all directions. This discovery could change the way we think about potential earthquake damage. Credit: Daniel Trogman, Victor Tsai/AGYU

“What happens when you have an earthquake is the pieces of broken rock inside the fault zone start moving like pin balls,” he said. Flowing pieces redirect energy randomly, but at low frequencies, seismic waves simply bypass the jagged geological chaos near the fault, traveling in a gentle four-leaf clover pattern just as physics predicted.

This means that on the surface, a person may feel the same vibration no matter where they are standing, but buildings – sensitive to low-frequency waves – will feel the earthquake more intensely within the lines of the four-leaf clover pattern.

Geophysicists have long known this pattern. It is taught in Seismology 101. But, so far, evidence of its impact has been scant. That’s because seismic waves refract over great distances regardless of frequency, smoothing out their differences and making earthquakes look the same in all directions.

Near the source of the earthquake, the pattern should be different. This is where the LASSO Matrix came in. Its stacked sensors recorded the earthquakes as they appeared, gathering measurements from hundreds of sites in northern Oklahoma that the USGS, which funded and published the array, made available free online.

To test their idea of ​​uneven vibration near errors, Trugman developed algorithms for filtering LASSO data. At lower frequencies, each earthquake exhibited a four-leaf clover pattern of vibration; At higher frequencies there was no clear pattern, just as Tsai expected.

Although the tremors recorded by the Lasso Array were barely perceptible, the physics driving them should be the same for stronger earthquakes. Scientists have already begun examining large faults to see if their age or shape can alter the intensity of Earth’s motion. Their goal is to build a catalog of earthquake zones, showing which faults can generate the strongest and most dangerous types of seismic waves.

We may never be able to predict earthquakes, but we can already know enough to prepare for more information: Daniel T. DOI: 10.1029/2021GL095022 Provided by The University of Texas at Austin

Quote: Seismic shockwave pattern may redirect earthquake damage (2021, November 16) Retrieved November 16, 2021 from https://phys.org/news/2021-11-seismic-shockwave-pattern-redirecting-earthquake.html

This document is subject to copyright. Notwithstanding any fair dealing 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