Why Japan Issued Its First-Ever 'Major Earthquake Warning' – And What It Means

Abstract

The Japan Meteorological Agency issued its first-ever “major earthquake warning” on Thursday.

The warning came after a 7.1-magnitude earthquake struck off the country's southern coast.

This increases the risk of a larger earthquake in the Nankai Zone, an underwater subduction zone that scientists believe is capable of producing earthquakes as strong as 9.1 on the Richter scale.

After a 7.1-magnitude earthquake struck Japan’s southern islands on Thursday, the country’s meteorological agency issued an ominous warning: Another, larger quake is possible, and the risk will be especially high over the next week. In its first-ever “major earthquake warning,” the agency said the risk of strong tremors and tsunamis was higher than usual in the Nankai Trough, a subduction zone that can produce quakes of magnitude 8 or 9. It said residents in the area should brace themselves.

The message wasn't a prediction, but a forecast of increased risk – and it shows how much progress seismologists have made in understanding the dynamics of subduction zone earthquakes.

Here's what you need to know about the situation.

dangerous subduction zone

The Nankai Trough is an underwater subduction zone where the Eurasian Plate collides with the Philippine Sea Plate, forcing the latter to subduct beneath the former and into the Earth's mantle.

Subduction zone faults cause pressure to build up, and what's called a megaquake occurs when a closed fault slips and releases that pressure. “Megaquake” is just a shortened version of the name. These zones have produced some of the most powerful earthquakes in Earth's history.

The Pacific “Ring of Fire” is a group of subduction zones. In the United States, the Cascadia subduction zone stretches off the west coast from Vancouver Island, Canada, to Cape Mendocino, California.

The Nankai Basin fault has several segments, but if the entire fault margin slipped at once, Japanese scientists believe the basin could produce an earthquake of up to magnitude 9.1.

A beach in Nichinan in southwestern Japan was closed on Friday, after the country issued its first warning of a possible major earthquake.

If a major earthquake were to occur near Japan, the Philippine Sea plate would shift, perhaps by 30 to 100 feet, near the country’s southeastern coast, causing severe shaking. The vertical displacement of the seafloor would trigger a tsunami and send waves toward Japan’s coast. Those waves could reach heights of nearly 100 feet, according to estimates by Japanese scientists published in 2020.

History of major earthquakes

A study last year suggested that the Nankai Trough produces large earthquakes roughly every 100 to 150 years. The Japan Earthquake Research Committee said in January 2022 that there was a 70% to 80% chance of a large quake in the next 30 years.

Large earthquakes in the Nankai Trough tend to occur in pairs, with the second quake often occurring within the following two years. The most recent examples were the “twin” earthquakes that struck the Nankai Trough in 1944 and 1946.

This phenomenon is due to the fragmented nature of the fault; when one part slips, it can put pressure on another part.

A magnitude 7.1 earthquake struck on Thursday in or near a subduction zone, the U.S. Geological Survey said.

People stand outside a building after leaving the building following an earthquake in Miyazaki on Thursday.

The 7.1-magnitude quake struck a part of the region that shakes more frequently than others, said Harold Tobin, a University of Washington professor who has studied the Nankai region. Regular quakes can release tension, so the possibility that the same part could trigger a major quake is not a major concern. The concern is the proximity of the quake to a part that has been building tension since the 1940s. “It’s adjacent to the western Nankai region, and that’s clearly locked in,” Tobin said. “That’s why we’re vigilant and concerned.”

Prediction, not prediction

Scientists cannot predict earthquakes, but they are working to develop the ability to predict times of increased danger, especially in areas that experience frequent shaking and have good monitoring equipment, such as Japan.

Firefighters walk past a collapsed building in Wajima, Ishikawa Prefecture, Japan, after an earthquake on New Year's Day.

Japanese authorities are asking residents to prepare, review evacuation routes and pay attention to possible future warnings. While the risk of a major earthquake is higher than usual, that doesn’t mean it’s happening anytime soon. The Japanese government’s warning guidelines say the chance of a major quake following a magnitude-7 quake within a week is “once in a few hundred,” according to a study last year.

The most likely outcome is that the last tremor will lead to nothing, although the possibility of a major earthquake is higher.

“We may have to wait decades before Nankai Island experiences another earthquake,” Tobin said.

Known risk

In 2011, an area of ​​the seafloor roughly the size of Connecticut shook all at once, triggering a 9.1-magnitude earthquake—the third-largest earthquake recorded worldwide since 1900. The massive quake triggered a tsunami off the east coast of Japan. More than 18,000 people were killed in the tsunami and earthquake, according to the U.S. National Oceanic and Atmospheric Administration.

The following year, the Japanese government reviewed natural disaster scenarios and found that about 323,000 people could die in a worst-case scenario for an earthquake in the Nankai Trough, mostly from tsunami effects.

The Cascadia subduction zone poses a similar risk to the U.S. West Coast, though large earthquakes there are less frequent—every 300 to 500 years. The fault has the potential to trigger a magnitude-9.1 earthquake and tsunami waves up to 80 feet high. Researchers recently mapped the fault in detail and found that it is divided into four segments.

This article was originally published on NBCNews.com.

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