Tag Archives: seismic

‘Dr. Phil’ To End After 21 Seasons Amid Seismic Changes In Syndication – Deadline

February 1, 2023 Admin Leave a comment

Another daytime fixture, Dr. Phil McGraw, is leaving after more than two decades as one of television’s most popular talk show hosts. His syndicated daytime show, Dr. Phil, will end its run of original episodes with the current 2022-2023 television season, the show’s 21st.

McGraw’s decision comes as his most recent contract is coming to an end. Dr. Phil received a five-season renewal in 2018 as part of a mega-deal extension with CBS Media Ventures, taking it through its current season.

It’s been a transformational year in the increasingly challenging daytime talk show landscape, with stalwarts The Ellen DeGeneres Show, The Wendy Williams Show, Maury, Dr. Oz as well as The Real all ending within the past 12 months.

CBS Media Ventures will offer stations library episodes of Dr. Phil for the 2023-24 season and beyond. They will include new content such as wrap-arounds and intros by McGraw, as well as guest updates.

I hear the distributor is aiming to keep Dr. Phil’s primetime periods for the repeats at the same or similar price, which is facing some initial resistance from stations. CBS Media Ventures did this successfully with Judge Judy after the 2021 end of the hit court show. Repeats are airing in the same time periods in most major markets, with Judge Judy as the No. 4 most-watched syndicated program currently, with little ratings erosion.

McGraw, the current doyen of daytime, began his TV career on The Oprah Winfrey Show in the late ’90s before headlining his own spinoff, produced by Winfrey’s Harpo Studios. Launching in September 2002, Dr. Phil was an instant hit, second in ratings only to Oprah. Following Winfrey’s departure from daytime in 2011, Dr. Phil took the crown as the most watched daytime syndicated talk show, which it kept for the past decade, only recently slipping to No. 2 behind Live with Kelly & Ryan.

“I have been blessed with over 25 wonderful years in daytime television,” McGraw said. “With this show, we have helped thousands of guests and millions of viewers through everything from addiction and marriage to mental wellness and raising children. This has been an incredible chapter of my life and career, but while I’m moving on from daytime, there is so much more I wish to do.”

With two other daytime syndicated shows executive produced by McGraw, The Doctors and Daily Mail TV, canceled last year, his decision to end Dr. Phil marks a final exit from daytime for the popular TV personality who, alongside his daytime career, has been building a track record in primetime, executive producing back-to-back successful CBS drama series in Bull and freshman So Help Me Todd.

In the immediate future, McGraw plans to focus on primetime programming with a new partnership, slated for an early 2024 launch.

“I am compelled to engage with a broader audience because I have grave concerns for the American family, and I am determined to help restore a clarity of purpose as well as our core values,” he said.

During its run, Dr. Phil, featuring McGraw tackling a different topic on each show and offering advice to his guests, has received 31 Emmy nominations and won five PRISM Awards for the accurate depiction of drug, alcohol and tobacco abuse and addiction, as well as a MADD (Mothers Against Drunk Drivers) Media Award.

“Phil is a valued partner and member of the CBS/King World family, and while his show may be ending after 21 years, I’m happy to say our relationship is not,” said Steve LoCascio, president of CBS Media Ventures. “Phil changed the daytime landscape as the force behind one of the most popular talk shows ever on daytime TV. We plan to be in the Dr. Phil business with the library for years to come and welcome opportunities to work together in the future.”

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Changes in Earth’s Outer Core Revealed by Seismic Waves From Earthquakes

July 2, 2022 Admin Leave a comment

A one-second discrepancy in the travel time of a set of seismic waves gives us an important and unprecedented glimpse of what’s happening deeper in the Earth’s interior.

Theory underpins our understanding of convection in the Earth’s outer core and its function in controlling the planet’s magnetic field. Convective flows or how they may be changing have never been directly observed by scientists. Virginia Tech geoscientist Ying Zhou puts proof forward for the first time.

A large earthquake shook the Kermadec Islands region in the South Pacific Ocean in May 1997. A little over 20 years later, in September 2018, a second big earthquake hit the same location, with its waves of seismic energy emanating from the same region.

Although two decades separated the earthquakes, because they occurred in the same region, they’d be expected to send seismic waves through the Earth’s layers at the same speed, said Ying Zhou, a geoscientist with the Department of Geosciences at the Virginia Tech College of Science.

The blue path illustrates a core-penetrating seismic wave moving through a region in the outer core, where the seismic speed has increased because a low-density flow has moved into the region. Credit: Virginia Tech’s Ying Zhou

However, in data recorded at four of more than 150 Global Seismographic Network stations that log seismic vibrations in real time, Zhou found a surprising anomaly among the twin events. During the 2018 earthquake, a set of seismic waves called SKS waves traveled about one second faster than their counterparts had in 1997.

According to Zhou, whose findings were published recently in

Blue lines are seismic rays in the outer core, where core-penetrating seismic waves moved through that region faster in 2018 than in 1997. Credit: Image courtesy of Ying Zhou

Scientists also have only been able to speculate about the source of gradual changes in strength and direction of the magnetic field that have been observed, which likely involves changing flows in the outer core.

“If you look at the north geomagnetic pole, it’s currently moving at a speed of about 50 kilometers (31 miles) per year,” Zhou said. “It’s moving away from Canada and toward Siberia. The magnetic field is not the same every day. It’s changing. Since it’s changing, we also speculate that convection in the outer core is changing with time, but there’s no direct evidence. We’ve never seen it.”

Zhou set out to find that evidence. The changes happening in the outer core aren’t dramatic, she said, but they’re worth confirming and fundamentally understanding. In seismic waves and their changes in speed on a decade time scale, Zhou saw a means for “direct sampling” of the outer core. That’s because the SKS waves she studied pass right through it.

“SKS” represents three phases of the wave: First it goes through the mantle as an S wave, or shear wave; then into the outer core as a compressional wave; then back out through the mantle as an S wave. How fast these waves travel depend in part on the density of the outer core that’s in their path. If the density is lower in a region of the outer core as the wave penetrates it, the wave will travel faster, just as the anomalous SKS waves did in 2018.

“Something has changed along the path of that wave, so it can go faster now,” Zhou said.

Ying Zhou of the Virginia Tech Department of Geosciences. Credit: Photo courtesy of Ying Zhou

To Zhou, the difference in wave speed points to low-density regions forming in the outer core in the 20 years since the 1997 earthquake. That higher SKS wave speed during the 2018 earthquake can be attributed to the release of light elements such as hydrogen, carbon, and oxygen in the outer core during convection that takes place as the Earth cools, she said.

“The material that was there 20 years ago is no longer there,” Zhou said. “This is new material, and it’s lighter. These light elements will move upward and change the density in the region where they’re located.”

To Zhou, it’s evidence that movement really is happening in the core, and it’s changing over time, as scientists have theorized. “We’re able to see it now,” she said. “If we’re able to see it from seismic waves, in the future, we could set up seismic stations and monitor that flow.”

What’s next

That’s Zhou’s next effort. Using a method of wave measurement known as interferometry, her team plans to analyze continuous seismic recordings from two seismic stations, one of which will serve as a “virtual” earthquake source, she said.

“We can use earthquakes, but the limitation of relying on earthquake data is that we can’t really control the locations of the earthquakes,” Zhou said. “But we can control the locations of seismic stations. We can put the stations anywhere we want them to be, with the wave path from one station to the other station going through the outer core. If we monitor that over time, then we can see how core-penetrating seismic waves between those two stations change. With that, we will be better able to see the movement of fluid in the outer core with time.”

Reference: “Transient variation in seismic wave speed points to fast fluid movement in the Earth’s outer core” by Ying Zhou, 25 April 2022, Communications Earth & Environment.
DOI: 10.1038/s43247-022-00432-7

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There’s a Change Happening to Earth’s Outer Core, as Revealed by Seismic Wave Data

July 1, 2022 Admin Leave a comment

Most of our knowledge about what sits at the center of our planet comes from the study of seismic waves rolling out from earthquakes. Careful analysis of these waves can reveal the composition of rocks and metal below Earth’s surface.

A new study of seismic waves propagating from two different earthquakes – in similar locations but separated by a gap of 20 years – has revealed changes that are happening in Earth’s outer core, the swirling layer of liquid iron and nickel between the mantle (the rock underneath the surface) and the inner core (the deepest layer).

The outer core and the iron contained within it directly influence our planet’s magnetic field, which in turn provides protection from space and solar radiation that would otherwise make life on Earth impossible.

That makes understanding the outer core and its evolution over time vitally important. The data recorded from four seismic wave monitors across both earthquakes showed that waves from the later event traveled around one second faster when passing through the same region of the outer core.

“Something has changed along the path of that wave, so it can go faster now,” says geoscientist Ying Zhou from Virginia Tech. “The material that was there 20 years ago is no longer there.”

“This is new material, and it’s lighter. These light elements will move upward and change the density in the region where they’re located.”

The types of waves analyzed here are SKS waves: they pass through the mantle as shear waves (the S), then into the outer core as compressional waves (the K), then out the other side and back through the mantle again as more shear waves (the second S). The timing of that travel can be revealing.

As for the two earthquakes, both were near the Kermadec Islands in the South Pacific Ocean – the first in May 1997 and the second in September 2018, giving researchers a unique opportunity to see how Earth’s core may have changed over time.

How seismic waves travel through the outer core. (Ying Zhou)

The convection occurring in the liquid iron of Earth’s outer core as it crystalizes onto the inner core creates flowing electrical currents, which is what controls the magnetic field around us. However, the relationship between the outer core and Earth’s magnetic field isn’t fully understood – a lot of it is based on hypothetical modeling.

“If you look at the north geomagnetic pole, it’s currently moving at a speed of about 50 kilometers [31 miles] per year,” says Zhou. “It’s moving away from Canada and toward Siberia. The magnetic field is not the same every day. It’s changing.”

“Since it’s changing, we also speculate that convection in the outer core is changing with time, but there’s no direct evidence. We’ve never seen it.”

This new study – and potentially future studies like it – could provide useful insights into exactly how the outer core and its convection are changing. While the changes noted here aren’t huge, the more we know, the better.

In this case, Zhou suggests that lighter elements such as hydrogen, carbon, and oxygen have been released in the outer core since 1997. It corresponds to a density reduction of around 2–3 percent and a convection flow speed of about 40 kilometers (25 miles) per hour, according to the published paper.

There are currently 152 Global Seismographic Network stations around the world, monitoring seismic waves in real-time. While we can’t control the location or timing of earthquakes, we can make sure that as much data as possible is logged about them.

“We’re able to see it now,” says Zhou. “If we’re able to see it from seismic waves, in the future, we could set up seismic stations and monitor that flow.”

The research has been published in Nature Communications Earth & Environment.

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Seismic waves from earthquakes reveal changes in the Earth’s outer core

June 24, 2022 Admin Leave a comment

In May 1997, a large earthquake shook the Kermadec Islands region in the South Pacific Ocean. A little over 20 years later, in September 2018, a second big earthquake hit the same location, its waves of seismic energy emanating from the same region.

Though the earthquakes occurred two decades apart, because they occurred in the same region, they’d be expected to send seismic waves through the Earth’s layers at the same speed, said Ying Zhou, a geoscientist with the Department of Geosciences in the Virginia Tech College of Science.

But in data recorded at four of more than 150 Global Seismographic Network stations that log seismic vibrations in real time, Zhou found an anomaly among the twin events: During the 2018 earthquake, a set of seismic waves known as SKS waves traveled about one second faster than their counterparts had in 1997.

According to Zhou, whose findings were recently published in Communications Earth & Environment, that one-second discrepancy in SKS wave travel time gives us an important and unprecedented glimpse of what’s happening deeper in the Earth’s interior, in its outer core.

What’s inside counts

The outer core is sandwiched between the mantle, the thick layer of rock underneath the Earth’s crust, and the inner core, the planet’s deepest interior layer. It’s composed mainly of liquid iron that undergoes convection, or fluid flow, as the Earth cools. This resulting swirling of liquid metal produces electrical currents responsible for generating the Earth’s magnetic field, which protects the planet and all life on it from harmful radiation and solar winds.

Without its magnetic field, the Earth could not sustain life, and without the moving flows of liquid metal in the outer core, the magnetic field wouldn’t work. But scientific understanding of this dynamic is based on simulations, said Zhou, an associate professor. “We only know that in theory, if you have convection in the outer core, you’ll be able to generate the magnetic field,” she said.

“If you look at the north geomagnetic pole, it’s currently moving at a speed of about 50 kilometers [31 miles] per year,” Zhou said. “It’s moving away from Canada and toward Siberia. The magnetic field is not the same every day. It’s changing. Since it’s changing, we also speculate that convection in the outer core is changing with time, but there’s no direct evidence. We’ve never seen it.”

Blue lines are seismic rays in the outer core, where core-penetrating seismic waves moved through that region faster in 2018 than in 1997. Credit: Ying Zhou

“Something has changed along the path of that wave, so it can go faster now,” Zhou said.

What’s next

Swarm satellites unveil magnetic waves that sweep the outermost part of Earth’s outer core

More information:
Ying Zhou, Transient variation in seismic wave speed points to fast fluid movement in the Earth’s outer core, Communications Earth & Environment (2022). DOI: 10.1038/s43247-022-00432-7

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retrieved 25 June 2022
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‘Monster’ Quake on Mars Is The Biggest Ever Recorded on Another Planet, NASA Says

May 11, 2022 Admin Leave a comment

In terms of seismic events on the red planet (or indeed any other planet besides Earth), this is the biggest one recorded so far: the NASA InSight lander has recorded a ‘monster’ of a marsquake, which is estimated to have hit magnitude 5 on the scale used on Earth.

That beats the previous record holder, a magnitude-4.2 marsquake that Insight recorded back on 25 August 2021. The new quake happened on Mars on May 4 of this year, the 1,222nd sol (or Martian day) of the lander’s mission.

A magnitude-5 quake on Earth would be classed as moderate, only causing minor damage. However, it’s right at the upper end of the size of quakes that scientists are discovering on Mars, due to less seismic activity.

The full marsquake spectrogram. (NASA/JPL-Caltech/ETH Zurich)

Right now we don’t know what caused the marsquake or where exactly on the red planet it originated from, but it’s already of intense interest for researchers. It adds to the more than 1,300 quakes that Insight has detected since landing in November 2018.

By studying the seismic waves traveling across Mars, scientists hope to learn more about the planet’s crust, mantle, and core. That in turn should inform understanding about how Mars (and other similar planets, such as Earth) formed in the first place.

“Since we set our seismometer down in December 2018, we’ve been waiting for ‘the big one’,” says planetary geophysicist Bruce Banerdt from the Jet Propulsion Laboratory (JPL) in California, and the leader of the InSight mission.

“This quake is sure to provide a view into the planet like no other. Scientists will be analyzing this data to learn new things about Mars for years to come.”

As marsquakes aren’t typically as violent as earthquakes, they’re more difficult to detect, and other vibrations – from the wind, for example – can interfere with readings. With that in mind, InSight is fitted with a highly sensitive seismometer called the Seismic Experiment for Interior Structure.

Volcanic activity is also thought to be generating seismic waves on Mars, and experts continue to identify new patterns in the data that Insight and its seismometer have already logged and beamed back to Earth.

With that in mind, you can expect to hear plenty more about the data collected by Insight on 4 May 2022, in the future, but for now it’s clear that the quake is a record-breaker – and way above average for what would normally be expected on Mars.

Unfortunately, Insight has now run into some technical difficulties: With the onset of the Martian winter and increased levels of dust in the air, the lander is struggling to get enough sunlight on the solar panels that power it up.

As a result, the machine has put itself into safe mode for the time being. This hibernation shuts down all but the most essential functions, and it may be some time before we hear anything from Insight again.

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Record-Breaking Earthquake Swarm Hits Antarctica as Sleeping Volcano Awakens

April 29, 2022 Admin Leave a comment

A long-dormant underwater volcano near Antarctica has woken up, triggering a swarm of 85,000 earthquakes.

The swarm, which began in August 2020 and subsided by November of that year, is the strongest earthquake activity ever recorded in the region. And the quakes were likely caused by a “finger” of hot magma poking into the crust, new research finds.

“There have been similar intrusions in other places on Earth, but this is the first time we have observed it there,” study co-author Simone Cesca, a seismologist at the GFZ German Research Centre for Geosciences in Potsdam, told Live Science.

“Normally, these processes occur over geologic time scales,” as opposed to over the course of a human lifespan, Cesca said. “So in a way, we are lucky to see this.”

The swarm occurred around the Orca Seamount, an inactive volcano that rises 2,950 feet (900 meters) from the seafloor in the Bransfield Strait, a narrow passage between the South Shetland Islands and the northwestern tip of Antarctica.

In this region, the Phoenix tectonic plate is diving beneath the continental Antarctic plate, creating a network of fault zones, stretching some portions of the crust and opening rifts in other places, according to a 2018 study in the journal Polar Science.

Scientists at the research stations on King George Island, one of the South Shetland Islands, were the first to feel the rumblings of small quakes. Word soon got back to Cesca and his colleagues around the world, some of whom were collaborating on separate projects with the researchers on the island.

The team wanted to understand what was going on, but King George Island is remote, with just two seismic stations nearby, Cesca said. So the researchers used data from those seismic stations, as well as data from two ground stations for the global satellite navigation system, to measure ground displacement.

They also looked at data from more far-flung seismic stations and from satellites circling Earth that use radar to measure shifting at ground level, the study authors reported April 11 in the journal Communications Earth & Environment.

The nearby stations are rather simple, but they were good for detecting the tiniest quakes. More distant stations, meanwhile, use more sophisticated equipment and can thus paint a more detailed picture of the larger quakes.

By piecing these data together, the team was able to create a picture of the underlying geology that triggered this massive earthquake swarm, Cesca said.

The two largest earthquakes in the series were a magnitude 5.9 quake in October 2020 and a magnitude 6.0 quake in November. After the November quake, seismic activity waned. The quakes seemed to move the ground on King George Island around 4.3 inches (11 centimeters), the study found.

Only 4 percent of that displacement could be directly explained by the earthquake; the scientists suspect the movement of magma into the crust largely accounts for the dramatic shifting of the ground.

“What we think is that the magnitude 6 somehow created some fractures and reduced the pressure of the magma dike,” Cesca said.

If there was an underwater eruption at the seamount, it likely happened at that time, Cesca added.

But as of yet, there is no direct evidence for an eruption; to confirm that the massive shield volcano blew its top, scientists would have to send a mission to the strait to measure the bathymetry, or seafloor depth, and compare it to historical maps, he said.

Related content:

Deepest earthquake ever detected should have been impossible

This article was originally published by Live Science. Read the original article here.

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Mars Is Rumbling With Mysterious Quakes We’ve Never Detected Before

April 5, 2022 Admin Leave a comment

It turns out that Mars is rumblier than we knew. New techniques have revealed previously undetected quakes beneath the Martian surface – and, scientists say, the best explanation so far is ongoing volcanic activity.

The evidence seems to be mounting that Mars is far from dead, but hosts, underneath its dusty, barren surface, an interior gurgling away with seismic activity.

“Knowing that the Martian mantle is still active is crucial to our understanding of how Mars evolved as a planet,” says geophysicist Hrvoje Tkalčić of the Australian National University in Australia.

“It can help us answer fundamental questions about the Solar System and the state of Mars’ core, mantle, and the evolution of its currently-lacking magnetic field.”

For a very long time, scientists believed that nothing much was going on inside Mars.

The planet has very little in the way of a magnetic field. Planetary magnetic fields are (usually) generated inside the planet, by something called a dynamo – a rotating, convecting, and electrically conducting fluid that converts kinetic energy into magnetic energy, spinning a magnetic field out into space.

Mars’ lack of a magnetic field suggests a lack of activity. This is a big deal; in fact, a magnetic field can mean the difference between life and death. Here on Earth, the magnetic field protects us from cosmic radiation that might destroy life. On Mars, radiation levels are much higher, even though it is more distant from the Sun.

“All life on Earth is possible because of the Earth’s magnetic field and its ability to shield us from cosmic radiation, so without a magnetic field life as we know it simply wouldn’t be possible,” Tkalčić explains.

But when NASA’s InSight lander arrived in November 2018 and started listening for Mars’ heartbeat, we learnt something really remarkable: Mars is rumbling. To date, InSight has detected hundreds of marsquakes – enough to give us a detailed map of the Martian interior.

Tkalčić and his colleague, geophysicist Weijia Sun of the Chinese Academy of Sciences, wanted to look for quakes that might have gone unnoticed in the InSight data. They used two unconventional techniques, only recently applied to geophysics, to hunt seismic events in the InSight data.

Based on nine templates of known marsquakes, the pair detected 47 new seismic events, coming from a region on Mars called the Cerberus Fossae – a system of fissures created by faults that have pulled the crust apart.

Most of those new seismic events resemble the waveforms of two notable Cerberus Fossae quakes that took place in May and July of 2019, suggesting that the smaller quakes are related to the larger ones.

Then the researchers sought to figure out the cause of the quakes. Their analysis found that there was no pattern to be found in the timing of the quakes, ruling out causes such as the influence of Martian moon Phobos.

“We found that these marsquakes repeatedly occurred at all times of the Martian day, whereas marsquakes detected and reported by NASA in the past appeared to have occurred only during the dead of night when the planet is quieter,” Tkalčić says.

“Therefore, we can assume that the movement of molten rock in the Martian mantle is the trigger for these 47 newly detected marsquakes beneath the Cerberus Fossae region.”

Previous analysis of features on the surface of Mars at the Cerberus Fossae found that the region had been volcanically active recently, within the last 10 million or so years.

The activity identified by Sun and Tkalčić, attributed to the repetitive movement of magma in the Martian mantle, also suggests that Mars is more volcanically and seismically active than we thought.

If this is the case, the results have implications for our understanding of the history of Mars – and its future.

“The marsquakes indirectly help us understand whether convection is occurring inside of the planet’s interior, and if this convection is happening, which it looks like it is based off our findings, then there must be another mechanism at play that is preventing a magnetic field from developing on Mars,” Tkalčić says.

“Understanding Mars’ magnetic field, how it evolved, and at which stage of the planet’s history it stopped is obviously important for future missions and is critical if scientists one day hope to establish human life on Mars.”

The research has been published in Nature Communications.

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The Iron of Earth’s Inner Core Could Be in a Strange ‘Superionic’ State, Study Finds

February 14, 2022 Admin Leave a comment

Deep below the crust of Earth, past the thick mantle and liquid outer core, lies a 1,220-kilometer (760 mile) ball of solid inner core.

But a new study has suggested that the inner core is not solid at all, instead forming a ‘superionic state’ with hydrogen, oxygen, and carbon, making it unlike either a liquid or a solid.

We can’t exactly drill down the 6,371 km (3,959 miles) to the center of the Earth to check what’s going on, so scientists use Earth’s natural drill – seismic waves from earthquakes – to understand the composition of our planet.

However, even with these measurements, the inner core remains somewhat of a mystery. In the 1930s, indirect evidence suggested it could be solid, and a few decades later it was thought to be a crystalline iron. But this incredibly hot, incredibly dense ball in the middle of our planet is still making us second guess what’s going on in there.

We know from seismic wave data that the inner core is soft, with a low shear-wave velocity, meaning it can’t just be solid iron or iron alloy. Some scientists think there could be a second inner inner core, while others think that due to the lighter density than would be expected by pure iron alone, there could be some light elements as an alloy.

But a new study, led by Yu He from the Chinese Academy of Sciences, has now investigated the potential phase of matter this mix of elements may exist in down, arriving at the suggestion that the ‘solid’ state of the core might really be a superionic state instead.

“We find that hydrogen, oxygen and carbon in hexagonal close-packed iron transform to a superionic state under the inner core conditions, showing high diffusion coefficients like a liquid,” the team writes in their new paper.

“This suggests that the inner core can be in a superionic state rather than a normal solid state.”

Superionic is another state of matter – alongside solid, liquid, and gas – but with distinct differences. In superionic water – which was recently made in a lab – extremely high temperatures and pressures break apart each water molecule, leaving the oxygen ions to form a solid, while the hydrogen ions float around more like a liquid.

In the hot inner core of Earth, the team used computer simulations of how seismic waves would travel through different combinations of elements, and discovered that alloys of iron with carbon, hydrogen, and oxygen could work the same way as superionic water.

The iron atoms were ‘solid’ in the crystalline lattice structure, whereas the carbon, hydrogen, and oxygen molecules would diffuse through the medium, creating the liquid-like element.

“It is quite abnormal,” said He. “The solidification of iron at the inner core boundary does not change the mobility of these light elements, and the convection of light elements is continuous in the inner core.”

This work is unlikely to be the last word on the subject. The paper’s conclusions give a good model for this softer and less dense pure iron, but it doesn’t answer another question about the inner core – why it is seemingly uneven throughout.

For that, we’ll just have to keep digging.

The research has been published in Nature.

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Mountain-Sized Rock Hidden Underneath Japan Could Be a Magnet For Megaquakes

February 8, 2022 Admin Leave a comment

A mountain-sized mass of igneous rock beneath the coast of southern Japan could be acting as a sort of magnet or lightning rod for huge earthquakes.

According to a new 3D visualization of the feature, known as the Kumano Pluton, the tectonic energy from megaquakes seems to be diverted to several points along its side.

This could help scientists better predict the impact of massive quakes in the region, as well as better understand how these igneous masses interact with tectonic activity.

“We cannot predict exactly when, where, or how large future earthquakes will be, but by combining our model with monitoring data, we can begin estimating near-future processes,” says geophysicist Shuichi Kodaira of the Japan Agency for Marine-Earth Science and Technology in Japan.

“That will provide very important data for the Japanese public to prepare for the next big earthquake.”

Hints of the Kumano Pluton were first revealed in 2006. It is, as the name suggests, a rock feature known as a pluton – an intrusion of igneous rock that displaces rock underground, slowly cooling and hardening in a large chunk.

(Adrien Arnulf)

Above: The Kumano Pluton appears as a red bulge (indicating dense rock) in the 3D visualization.

Seismic imaging revealed that there was something of a different density to the surrounding rock on the Nankai subduction zone; that’s the region along which one tectonic plate slips beneath the edge of another, accompanied by heightened earthquake and volcanic activity. Numerical simulations helped reveal that the chunk was plutonic.

But the true extent of it remained unexplored. Now, using 20 years’ worth of seismic data from the Nankai subduction zone, a team of researchers has mapped the entirety of the Kumano Pluton.

Quakes and tremors, while destructive, can also be a very powerful tool, you see. Quakes are quite marvelous things, really. They ripple out from their point of origin, propagating through the planet, and bouncing around.

The way these seismic waves travel through and reflect off certain materials allows seismologists to map structures we can’t see deep underground.

It was painstaking work, comprising not just the millions of seismic recordings from Japan’s network of earthquake sensors, but also those of other passing scientific surveys, for the largest seismic data set ever created.

The vast amount of data the team compiled on the Nankai subduction zone was fed into the LoneStar5 supercomputer at the University of Texas at Austin to generate a high-resolution 3D model of the pluton. Fascinatingly, it revealed features we hadn’t seen before.

The model shows that the pluton’s weight is causing Earth’s crust beneath it to bend under the strain, and bulge upward slightly above it. Surprisingly, the pluton seems to be providing a pathway for groundwater to seep beneath Earth’s crust into the upper mantle by exacerbating the bending of Earth’s crust.

Cross section showing the origin of the 1944 quake. (Arnulf et al., Nat.Commun., 2022)

Because the Kumano Pluton is so dense and rigid, it is also likely playing a significant role in tectonic activity.

Huge earthquakes with magnitudes higher than 8 originated on the flanks of the pluton in 1944 and 1946. Given that subducting slabs are highly sensitive to variations in structure, the pluton is likely having a profound effect on both the geometry and tectonic activity in the region.

The team hopes that their discovery will prompt thorough investigations into the subterranean structures that might be hiding in other subduction zones.

“The fact that we can make such a large discovery in an area that is already well studied is, I think, eye opening to what might await at places that are less well monitored,” says geophysicist Adrien Arnulf of the University of Texas Institute for Geophysics.

The research has been published in Nature Geophysics.

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Mysterious Anomalies Deep Within Our Planet May Have Lingered Since Earth’s Creation

January 5, 2022 Admin Leave a comment

Chemical leftovers from the very earliest days of our planet could still be present near Earth’s core, according to new research, and the discovery could improve our understanding of plate tectonics phenomena happening today.

The team behind the study compares these leftovers to clumps of flour at the bottom of a bowl of batter – elements that haven’t been properly mixed over the course of billions of years, which show up as anomalies on seismic wave readings.

We know that seismic waves slow to a crawl near the core of the Earth, going through what are known as ultra-low velocity zones (ULVZs). The big question is what are these zones made out of – and scientists now think they might have found the answer.

“This finding changes our view on the origin and dynamics of ultra-low velocity zones,” says seismologist Surya Pachhai from the Australian National University.

“We found that this type of ultra-low velocity zone can be explained by chemical heterogeneities created at the very beginning of the Earth’s history and that they are still not well mixed after 4.5 billion years of mantle convection.”

The way that seismic waves echo through Earth’s mantle and crust give us clues about their composition, but measuring down through around 2,900 kilometers or 1,800 miles of rock isn’t easy. To address that, the scientists used a reverse-engineering approach, running hundreds of thousands of computer simulations, using a process known as Bayesian inversion.

By comparing these models to actual readings taken from underneath the Coral Sea between Australia and New Zealand, the team was able to narrow down the possibilities of what the ULVZs just above the liquid metal outer core could be made of.

The researchers suggest that the ULVZs could be partly made of iron oxide – we know it as rust, but it acts as a metal deep in the mantle. It also now looks likely that this section of our planet is made up of several sublayers, something which hasn’t been suspected for these zones before.

This layering could well have been caused by a planetary object the size of Mars smashing into the early Earth. The event is thought to have thrown up debris that formed the Moon, and it’s also likely to have created an ocean of magma, made up of rock, gases, and crystals, which could have sunk down to its current position over billions of years.

“The physical properties of ultra-low velocity zones are linked to their origin, which in turn provides important information about the thermal and chemical status, evolution and dynamics of Earth’s lowermost mantle – an essential part of mantle convection that drives plate tectonics,” says Pachhai.

Seismic waves are known to slow by up to a half in ULVZs, with corresponding density going up by a third. It has been suggested that these are partially melted areas of the mantle, providing magma for volcanic hot spots on the surface (such as Iceland).

However, not all of the high-density zones match up with places of frequent volcanic activity, which suggests something else is going on. That inspired the research team to take a closer look – revealing the surprising layers that make up these ULVZs, with the help of computer modeling.

The mantle and the ULVZs at the bottom of it can drive the movement of tectonic plates close to the surface, which means the new research doesn’t just teach us more about the birth of the Earth, but also more about how it’s behaving today.

“Of all of the features we know about in the deep mantle, ultra-low velocity zones represent what are probably the most extreme,” says geologist Michael Thorne from the University of Utah.

“Indeed, these are some of the most extreme features found anywhere in the planet.”

The research has been published in Nature Geoscience.

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