Machine learning helps geoboffins spot huge beds of hot rocks 1,000km across deep below Earth's surface

Large structures were detected as anomalies in seismic waves processed by an algorithm

Geophysicists have uncovered large swathes of hot, dense rock lying nearly 3,000 kilometers beneath Earth's surface, hidden below the Pacific Ocean, thanks to an unsupervised learning algorithm.

These structures, described as "ultralow-velocity zones" (ULVZs) in a study published in Science on Friday, were detected by measuring the echoes of seismic waves emitted from earthquakes underground. "Ultralow-velocity zones are areas of unusually dense, hot material at the core-mantle boundary," Doyeon Kim, first author of the paper and a scientist at Cornell University, explained to The Register: "Seismic waves travel up to 30 per cent slower in ULVZs than through surrounding mantle materials."

The reflections of these seismic signals reveal that there are obstacles in the way as the waves travel in between the source of the earthquake and reach the seismometer. By studying the recordings and measuring the amount of diffraction in the echoes, the researchers can estimate how dense or large these objects are.

"We found echoes on about 40 per cent of all seismic wave paths," said Vedran Lekić, co-author of the study and an associate professor of geology at the University of Maryland. "That was surprising because we were expecting them to be more rare, and what that means is the anomalous structures at the core-mantle boundary are much more widespread than previously thought."

Some of the large areas of rock had previously been discovered, but there were new regions that haven't been seen before, like the one lurking below the Marquesas Islands, a tiny group of volcanic islands in the middle of the Southern Pacific Ocean. The team also found that the ultralow-velocity zone underneath the Hawaiian Islands is much larger than previously thought.

"The scale of typical ULVZs found elsewhere are on the order of about 100km. But what we discuss in our paper is an order of magnitude larger than those typical ULVZs, a structure about 1,000km across. ULVZs of this extraordinary size are called 'mega-ULVZs'. We detected two mega-ULVZs, one beneath Hawaii and the other beneath Marquesas Islands, both are located near the edge of the Pacific LLSVPs," Kim told us.

The team collected 7,000 seismogram recordings of the echoes and fed them to a machine-learning algorithm known as Sequencer. Developed by researchers at Tel Aviv University and John Hopkins University, the algorithm uses unsupervised learning to "reveal the main trend or sequence in a dataset." In other words, Sequencer is good at highlighting any anomalies – or the echoes – in data.

"Machine learning in earth science is growing rapidly and a method like Sequencer allows us to be able to systematically detect seismic echoes and get new insights into the structures at the base of the mantle, which have remained largely enigmatic," said Kim.

The researchers don't know what these structures are made out of and how they might affect Earth's plate tectonics over time. "Although still enigmatic we think all of these lower mantle structures are somewhat dynamically related as our mantle convects and the Earth keeps cooling down," he concluded.

"This mantle convection is the driving mechanism for hotspot volcanism and plate tectonics. And the Earth is the only terrestrial planet in our solar system where we uniquely observe plate tectonics and rarely observe such manifestation of volcanisms seen from the surface. Therefore, understanding mantle structures and their characteristics is important to learn how the Earth has evolved or evolving as opposed to other planets." ®

Broader topics

Other stories you might like

  • Stolen university credentials up for sale by Russian crooks, FBI warns
    Forget dark-web souks, thousands of these are already being traded on public bazaars

    Russian crooks are selling network credentials and virtual private network access for a "multitude" of US universities and colleges on criminal marketplaces, according to the FBI.

    According to a warning issued on Thursday, these stolen credentials sell for thousands of dollars on both dark web and public internet forums, and could lead to subsequent cyberattacks against individual employees or the schools themselves.

    "The exposure of usernames and passwords can lead to brute force credential stuffing computer network attacks, whereby attackers attempt logins across various internet sites or exploit them for subsequent cyber attacks as criminal actors take advantage of users recycling the same credentials across multiple accounts, internet sites, and services," the Feds' alert [PDF] said.

    Continue reading
  • Big Tech loves talking up privacy – while trying to kill privacy legislation
    Study claims Amazon, Apple, Google, Meta, Microsoft work to derail data rules

    Amazon, Apple, Google, Meta, and Microsoft often support privacy in public statements, but behind the scenes they've been working through some common organizations to weaken or kill privacy legislation in US states.

    That's according to a report this week from news non-profit The Markup, which said the corporations hire lobbyists from the same few groups and law firms to defang or drown state privacy bills.

    The report examined 31 states when state legislatures were considering privacy legislation and identified 445 lobbyists and lobbying firms working on behalf of Amazon, Apple, Google, Meta, and Microsoft, along with industry groups like TechNet and the State Privacy and Security Coalition.

    Continue reading
  • SEC probes Musk for not properly disclosing Twitter stake
    Meanwhile, social network's board rejects resignation of one its directors

    America's financial watchdog is investigating whether Elon Musk adequately disclosed his purchase of Twitter shares last month, just as his bid to take over the social media company hangs in the balance. 

    A letter [PDF] from the SEC addressed to the tech billionaire said he "[did] not appear" to have filed the proper form detailing his 9.2 percent stake in Twitter "required 10 days from the date of acquisition," and asked him to provide more information. Musk's shares made him one of Twitter's largest shareholders. The letter is dated April 4, and was shared this week by the regulator.

    Musk quickly moved to try and buy the whole company outright in a deal initially worth over $44 billion. Musk sold a chunk of his shares in Tesla worth $8.4 billion and bagged another $7.14 billion from investors to help finance the $21 billion he promised to put forward for the deal. The remaining $25.5 billion bill was secured via debt financing by Morgan Stanley, Bank of America, Barclays, and others. But the takeover is not going smoothly.

    Continue reading

Biting the hand that feeds IT © 1998–2022