Speed ​​kills: Speed ​​earthquakes that may destroy are more common

A global survey of large slope earthquakes (greater than 6.7 magnitude) showed that over a 20-year period, 14 percent of these earthquakes maintain ultrahigh rupture velocities.

By Laura Vattaroso, Simpson Strong Tie Fellow (@labtalk_laura)

Citation: Fattaruso, L., 2022, Supershear Earthquakes Are More Common Than We Thought, Temblor, http://doi.org/10.32858/temblor.289

Phenomena known as superquakes — those that travel at breakneck speed and can cause more shaking than slow quakes — may be more common than previously expected, according to a study of global earthquake data recently published in the journal Nature.

Superquakes occur when the frontal rupture of an earthquake moves faster than the seismic waves it produces. The rupture front is the leading edge of the fault plane of the fracture that generates the earthquake. The rapid advance of the rupture front causes the waves to pile together and form a much larger wave, known as a Mach cone wave – the earthquake’s equivalent of a sonic boom. The Mach cone wave generates waves of greater amplitude that produce a stronger shaking than a typical earthquake. The authors of the new study suggest that seismic risk estimates for the faults should take into account whether they could produce more super damaging hearing aids.

Global map of suspected and confirmed super-earthquakes. The yellow dots are large slip quakes that have not shown ultrahigh rupture velocities. Credit: Bao et al., 2022

Long, straight and cumbersome

According to Lingsen Meng, a UCLA seismologist and co-author of the study, the most likely candidates to host such earthquakes are long, straight, stressed, mature slip faults (which means they have caused many earthquakes before). According to Meng, the San Andreas fault in California, the North Anatolian fault in Turkey, and the Alpine fault in New Zealand are all examples of faults that meet the criteria.

The first direct measurements of super-seismicity were in 1999 when two super-earthquakes hit the North Anatolian Fault in Turkey, first in Izmit and then in Duzce (also the site of the earthquake in late November 2022). The 7.6-magnitude İzmit earthquake on August 17, 1999 was one of the deadliest earthquakes in recent Turkish history, and was followed a few months later by the 7.2-dozce earthquake on November 12, with two different earthquakes. North Anatolian Fault Sections.

In 2018, an earthquake measuring 7.5 on the Richter scale struck the Indonesian island of Sulawesi, including the capital, Palu. The earthquake caused the earth to behave like a liquid (called liquefaction), and triggered mudflows and landslides that resulted in widespread and severe damage from shaking. This earthquake also caused a much larger than expected tsunami due to the slip rupture. Sliding earthquakes do not usually produce the necessary vertical motion that displaces water and causes tsunamis. While some researchers concluded that landslides triggered by liquefaction triggered an unexpectedly large tsunami (Sasa and Takagawa, 2019), others concluded that sea floor uplift along the fault combined with enhanced vibration from super shear rupture was the cause ( Ulrish et al., 2019).

How weird are the events of Supershear?

To estimate the global prevalence of these extreme events, the researchers focused on earthquakes greater than magnitude 6.7. While smaller earthquakes can also reach super velocities, current methods of monitoring can only identify super audible ruptures that last 50 kilometers (31 miles) or more, which means that at the moment, only these larger earthquakes will have a rupture. detectable excessive.

Of the 87 large gliding earthquakes that occurred between 2000 and 2020, 12 showed breakneck velocities. From this data, the researchers estimate that about 14 percent of large strike earthquakes reach breakneck speeds, more than double the previous estimate of about 6 percent.

The Indonesian island of Sulawesi suffered widespread damage from a 7.5-magnitude earthquake in 2018. Credit: Ungkeito, CC BY-SA 4.0 via Wikimedia Commons

Using new methods that improve estimates of discrete travel velocities from distant quakes, researchers have found four previously unidentified superquakes. All of the newly identified superquakes occurred on ocean faults. Previous estimates of how super-quakes propagated underwater faults did not include, but the ocean floor is home to many long slip faults – the exact type of fault that can generate this type of rupture. By looking at earthquakes from both continental and oceanic sources, the researchers provided a clearer picture of how common these events are.

“There has never been a global survey like this because we didn’t have enough tools available before,” explains Ming.

The study used multiple methods to identify super-seismicity. Back projection—a method first developed for use with sonar and radar data—has been developed and honed as a method in seismology, enabling better resolution of rupture velocities. Using the arrival times of P waves at different seismic stations around the planet, the travel velocity of an earthquake rupture front can be estimated. When the back projection showed supersonic velocities, the researchers also looked for the Mach cone wave in the seismic data, which produces a distinct pattern of vibration compared to slower earthquakes.

From theory to observation

“In general, monitoring rupture velocity is challenging,” says Elif Ural, a seismic geotechnical engineer at Caltech who was not involved in the study. Super-earthquakes were predicted by numerical models and observed in laboratory experiments resulting in plastic fractures before measuring instruments existed on Earth’s surface. Determining whether they actually occur has been controversial in the past, but over the past two decades, methods of measuring them have improved. “An emerging back-projection technique that has been applied to large earthquakes, such as the Indonesian earthquake in Palu, reduces doubt and highlights that this phenomenon does indeed occur,” Ural explains. “Now we can monitor it better.”

While the study answered some questions about the global prevalence of these events, there are still many outstanding questions. Several superlattice events have been identified in the Caribbean on rifts that have oceanic crust on one side and continental crust on the other, suggesting that the adjacency of different materials across the rift may also promote ultrafast ruptures. The theory behind super-quakes suggests that they must move above a certain speed to maintain their high-speed propagation. However, many of the earthquakes observed in the latest study moved slower than that threshold, opening questions about what might be missing in the theory. Meng suggests that damage along pre-existing fault zones could be one explanation for this discrepancy. The global survey paved the way for future investigations of super-earthquakes and the conditions that enhance them.

Several earthquakes in California’s history have been suspected or proven to reach breakneck speeds, including the 1992 Landers earthquake and the 1979 Imperial Valley earthquake. Simulations of the Great San Francisco Earthquake of 1906 (shown here) indicate that it was also likely a paranormal event (Song et al., 2008). With so many faults capable of producing earthquake earthquakes large enough to reach ultra-high rupture velocities, understanding how super-rupture enhances vibration will be crucial for future disaster planning in the region. Photo: San Francisco in the aftermath of the 1906 earthquake and subsequent fires. Credit: US National Archives.

Laura Vattaroso is a classmate of Temblor’s Strong Tie Simpson. They have a Ph.D. candidate at U Mass Amherst, where they study how rocks fracture to better understand seismic processes (laurafattaruso.com). Simpson Strong Tie sponsors a Science Writing Fellow to cover important earthquake news around the world.

References

Bao, H., Xu, L., Ming, L. et al. Global frequency of oceanic and continental earthquakes. nat. geosci. 15, 942-949 (2022). https://doi.org/10.1038/s41561-022-01055-5

Sassa, S., & Takagawa, T. (2019). Tsunamis caused by liquefied gravity flow: First evidence and comparison from Indonesia’s 2018 Sulawesi earthquake and tsunami. Landslides, 16(1), 195-200.

Song SG, Beroza GC, & Segall P (2008). Standardized Source Model of the 1906 San Francisco Earthquake. Bulletin of the American Seismological Society, 98(2), 823-831.

Ulrich, T., Vater, S., Madden, E.H., Behrens, J., van Dinther, Y., Van Zelst, I.,… & Gabriel, A.A. (2019). Dual physics-based modeling reveals that seismic displacements are essential for the 2018 Palu, Sulawesi tsunami. Pure and Applied Geophysics, 176(1), 4069-4109.

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