Violent earthquakes are more common than previously thought

Aerial view of the San Andreas Fault between Bakersfield and Santa Barbara. Credit: Carol M. Highsmith/Library of Congress

Super strong earthquakes, once considered rare, are becoming more common than previously thought, according to a study led by UCLA geophysicists and published today in Nature Geoscience.

Scientists analyzed all earthquakes of magnitude 6.7 or greater around the world since 2000 — there were 87 in all — and identified 12 supershears, or about 14%. (Four of those earthquakes have not been previously reported.)

This percentage is more than double what scientists expected; To date, less than 6% of slope earthquakes have been identified as super seismic.

Slip-slip earthquakes occur when the edges of two tectonic plates rub against each other. Super earthquakes are a subtype of that group that occurs when subsurface faults erupt faster than shear waves – seismic waves that shake the Earth back and forth – can move through rock. The impact affects the energy that is then violently released; The effect can be compared to a sonic boom.

As a result, super earthquakes tend to produce more vibrations, and are possibly more destructive than other earthquakes of the same magnitude.

“When an airplane flies faster than sound can travel through the air, a cone of pent-up sound waves forms in front of the plane and when you catch up with it, we hear it all at once,” said Lingsen Meng, Leon and Joanne VC of the University of California. Knopov Professor of Physics and Geophysics, and corresponding author of the paper. “Ultrasonic earthquakes are likely to be more destructive than other types of earthquakes because they are more efficient at generating seismic waves, with more vibrations, which can cause more damage.”

The research also found that super earthquakes occur as commonly under the oceans as they do on land, and that they are more likely to occur along slip faults, such as the San Andreas Fault in California.

The results suggest that disaster planning efforts should take into account whether nearby faults are capable of causing ultra-high earthquakes and, if so, take measures to prepare for a higher level of vibration and potential damage than non-super earthquakes can cause.

The reason why there are relatively few super earthquakes, Meng said, is because researchers mainly study earthquakes on Earth.

The paper’s co-authors are Han Bao and Liu Xu of UCLA, and Jean-Paul Amberau, senior researcher at the University of the Côte d’Azur in Nice, France.

The scientists used a method called backproject to determine the direction in which the seismic waves arrived to infer how fast the earthquake was moving along the fault. This technique applies an algorithm to analyze the short time delay between seismic waves as they are detected by an array of sensors. This method is similar to how a person can be located by tracking the signals their smartphone sends to cell towers.

The data revealed that super earthquakes tend to occur on mature slip faults, where the edges of the two continental plates rub laterally against each other. In a mature fault, this action takes place long enough to create an area of ​​damaged rock that acts like a dam around the fault, slowing or preventing the spread of seismic waves and focusing their energy.

The findings could help scientists better understand what it takes for a fault to produce the kinds of ruptures that lead to super earthquakes, Ambero said.

In the past century, at least one major earthquake has occurred in California: In 1979, a 6.5-magnitude earthquake in Southern California’s Imperial Valley injured people as far away as Mexico and caused extensive damage to irrigation systems. And although it preceded scientific observation, the 1906 earthquake that caused massive damage in San Francisco also fell into the supershear category.

Not all ultrasonic earthquakes are catastrophic. The shape of the fault, the surrounding rocks, and other factors can affect the propagation of seismic waves and limit the accumulation of energy. Faults that bend tend to slow, deflect, or absorb seismic waves, while straight faults allow them to flow freely.

In an earlier study, Meng’s research group identified the catastrophic 7.5-magnitude earthquake that struck the Indonesian island of Sulawesi in 2018 as a supernatural event. The earthquake and tsunami that followed killed at least 4,000 people. Despite the bend in the Indonesian earthquake fault, the horrific damage occurred because the fault moved faster than any fault previously recorded and it is likely that energy from previous earthquakes was stored in the rock, waiting for the moment to erupt, Meng said.

Fortunately, Meng said, super-quakes in the ocean are less likely than earthquakes that cause the sea floor to move vertically to produce tsunamis.

On the other hand, the San Andreas fault is mostly straight and can experience a more explosive rupture than the Sulawesi earthquake.

More information: Han Bao et al, Global frequency of oceanic and continental super seismicity, Nature Geoscience (2022). DOI: 10.1038 / s41561-022-01055-5

Provided by University of California, Los Angeles

Quote: Super violent earthquakes are more common than previously thought (2022, November 1) Retrieved on November 2, 2022 from https://phys.org/news/2022-11-violent-supershear-earthquakes-common-previously.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