Connect with us

Uncategorized

The longest known earthquake lasted 32 years

 


The devastating earthquake that shook the Indonesian island of Sumatra in 1861 was long thought to be a sudden crack of an earlier fault. But new research found that the tectonic plates below the island had been slowly and quietly wrestling against each other for 32 years before the catastrophic event occurred.

This silent, decades-long earthquake – known as the “slow slide event” – was the longest chain of its kind ever discovered. It was so subtle and gradual that it went unnoticed along its trajectory, but a new study suggests that it may have precipitated a massive 1861 earthquake with a magnitude of at least 8.5, which in turn triggered a tsunami that killed thousands of people. The new study could help today’s scientists monitor dangerous earthquakes more effectively.

Like the most famous type of earthquake we feel shaking the Earth’s surface, slow earthquakes occur when two parts of the crust move against each other. Some faults are now monitored for slow slip using seismic instruments or GPS technology, but tracking such events on remote faults (or before the 1990s, when GPS became available) is extremely difficult. The most recent slow slide events studied by scientists lasted for hours, days, or weeks, with only a few years on. Kevin Furlong, a geologist at Pennsylvania State University who was not involved in the new research, says the decades-long slow slide “indicates that subduction zones are more diverse than we would necessarily have estimated.” (Subduction zones are regions where oceanic crust slides under continental crust.)

Near the Indonesian island of Simeulue off the coast of Sumatra, coral growth patterns record the up and down movements along the fault caused by the 1861 earthquake, providing a rare window into the past. Corals cannot grow when exposed to air. So, when local sea level changes as a result of tectonics, those changes appear in records of coral skeletal growth, says Reshav Malik, a doctoral student at Nanyang Technological University in Singapore and lead author of the new study published this month in Natural Geosciences. Simeulue reefs have an almost annual history of vertical movement at fault from 1738 to 1861.

The reefs reveal that Simeulue has been declining or sinking for 90 years at a steady rate of one or two millimeters per year, which is consistent with the rift background movement. But around 1829 it suddenly began to sink at five to seven times faster – in some years as much as a centimeter, Malik says. This indicates that the fault is starting to move in a slow-sliding earthquake. “It’s a very sharp change,” he says. This “rapid” decline continued until the massive earthquake of 1861.

Furlong says the study sheds light on the complexity of subduction zones. He notes for a long time, “the assumption was that between large earthquakes the system was simple”: two sections of the crust are locked against each other at fault, creating a stress formation until – it cracks – breaks loose with the ground – trembles.

Slow slip events complicate this picture. Malick says they may also act as triggers for larger earthquakes that can be detected by relieving pressure on one part of the fault while adding stress to adjacent sections. “It’s like a bunch of springs,” he explains. “So, if one of them gets fired, the others have to bear that burden.”

Malick says the 2004 Indian Ocean earthquake and tsunami that killed more than 220,000 people was preceded by a few years of slow slide in the Andaman Islands. However, slow slip could not help predict larger earthquakes because the duration of the slip varies so much. There are no defects detected by GPS for 32 years in a row, so modern surveillance may not be relaying events as long-term as the slow slide in 19th-century Indonesia. Not all faults are well monitored. This is particularly true for sub-ocean subduction faults, which require special monitoring of the sea floor rather than a Global Positioning System (GPS).

If the slow slip motion is ignored, researchers may miscalculate where the strains are at fault – and how strong the earthquake could produce that fault. “Once we can better define the closed area, we can better determine the size of the earthquake that would happen,” Furlong says.

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]