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(National Geographic)   Scientists detect deepest earthquake ever 467 miles beneath japan. Coming up next: Either Godzilla or C'thulhu   (nationalgeographic.com) divider line
    More: Interesting, Earthquake, Earth, Crust, deepest quakes of its size, lower mantle, hints of lower mantle quakes, part of the study team, series of peculiar earthquakes  
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280 clicks; posted to STEM » on 25 Oct 2021 at 4:38 PM (6 weeks ago)   |   Favorite    |   share:  Share on Twitter share via Email Share on Facebook



10 Comments     (+0 »)
View Voting Results: Smartest and Funniest
 
2021-10-25 3:57:28 PM  
So not just Morlocks... Evenmorelocks.
 
2021-10-25 4:02:33 PM  

ImpendingCynic: So not just Morlocks... Evenmorelocks.


Just Mycon Deep Children enjoying a burrito.
 
2021-10-25 4:47:33 PM  
uh oh
upload.wikimedia.orgView Full Size
 
2021-10-25 5:17:16 PM  
I'm not giving you my email address to keep reading.
 
2021-10-25 5:28:10 PM  

Insult Comic Bishounen: I'm not giving you my email address to keep reading.


Sad thing is the entire article is there in the page source... farking browsers conspire with Disney to make me once again pine for pine.
 
2021-10-25 5:39:56 PM  
Article is too big to C&P but this might be the interestingest part:

The upper mantle is rife with the sparkly green mineral olivine, but at greater depths, the mineral's crystal structure is no longer stable. Starting some 410 kilometers (255 miles) down, the atoms may rearrange into the minerals wadsleyite or ringwoodite, which grow increasingly common with depth. The olivine's transformation within the slab could create weak points in the rock where it can rapidly deform, generating a deep earthquake.
But around 660 kilometers (410 miles) down, the system abruptly changes. The dance of seismic waves around this boundary suggests the rocks below are much denser than those above-the beginning of the lower mantle.

In this layer, the earthen-hued mineral bridgmanite dominates, and the earthquake-generating transformations of olivine that can occur above no longer happen. So if a quake did strike in this layer of the planet, something else must have triggered it.

One possibility is the transformation of a different mineral within the sinking slab, such as the sepia-toned mineral enstatite. But Kiser and his colleagues also spotted another possible trigger in the movements of the slab.

The tiny aftershocks following the magnitude 7.9 quake seem to have occurred near the base of a torn slab of subducted Pacific seafloor that pierced the top of the lower mantle. The team suggests the large quake could have caused part of the mangled slab to settle slightly-"we're talking very, very slightly," Kiser says. That small shift might have been enough to concentrate stresses at the base of the slab as it plunged into the denser lower mantle rocks.

One way such an increase in stress could lead to the deep quake is by slightly deforming the rocks, which can generate heat and weaken them. The process could have kicked off a feedback loop, causing the rock to deform faster and faster as it grows hotter and weaker until the blocks rapidly shift in an earthquake. The building heat might have even generated melt that acted as a lubricant for the slip, Billen says.

Further analysis and modeling of the sinking slab's structures and the positions of aftershocks from the magnitude 7.9 event could help decipher the mechanism of not only this event but other deep earthquakes. "Maybe they cannot be explained by one single mechanism," says Haijiang Zhang, a seismologist at the University of Science and Technology of China
 
2021-10-25 5:43:19 PM  

KarmicDisaster: uh oh


"Oh, no" is the phrase. As in...

Oh, no.  They say he's got to go.  Go, go Gojira.  Oooh.
 
2021-10-25 7:27:39 PM  
My money's on C'thulhu.
 
2021-10-25 9:15:06 PM  
Meme bomb, because I hope it's Cthulhu and the Lost City rising to eat us all, sanity first and I can't decide which to go with.

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2021-10-25 10:35:04 PM  

Randrew: Article is too big to C&P but this might be the interestingest part:

The upper mantle is rife with the sparkly green mineral olivine, but at greater depths, the mineral's crystal structure is no longer stable. Starting some 410 kilometers (255 miles) down, the atoms may rearrange into the minerals wadsleyite or ringwoodite, which grow increasingly common with depth. The olivine's transformation within the slab could create weak points in the rock where it can rapidly deform, generating a deep earthquake.
But around 660 kilometers (410 miles) down, the system abruptly changes. The dance of seismic waves around this boundary suggests the rocks below are much denser than those above-the beginning of the lower mantle.

In this layer, the earthen-hued mineral bridgmanite dominates, and the earthquake-generating transformations of olivine that can occur above no longer happen. So if a quake did strike in this layer of the planet, something else must have triggered it.

One possibility is the transformation of a different mineral within the sinking slab, such as the sepia-toned mineral enstatite. But Kiser and his colleagues also spotted another possible trigger in the movements of the slab.

The tiny aftershocks following the magnitude 7.9 quake seem to have occurred near the base of a torn slab of subducted Pacific seafloor that pierced the top of the lower mantle. The team suggests the large quake could have caused part of the mangled slab to settle slightly-"we're talking very, very slightly," Kiser says. That small shift might have been enough to concentrate stresses at the base of the slab as it plunged into the denser lower mantle rocks.

One way such an increase in stress could lead to the deep quake is by slightly deforming the rocks, which can generate heat and weaken them. The process could have kicked off a feedback loop, causing the rock to deform faster and faster as it grows hotter and weaker until the blocks rapidly shift in an earthquake. The building hea ...


This is National Geographic. Not even National Geologic. The opinions are certainly fine and interesting, but they are more fluffy and speculative than instructive or prescriptive.

They are mostly referring to asperities, and as they subduct, they will melt and a greater or lesser rate. Those behaviors will be various. I am not surprised that some dense materials ground on each other at some great depth.

Good on the scientists and all that, but the blurb above amounts to a lot of more or less informed speculation. Information from sensors like this is so much more scarce than one could get about space using a telescope or about the ocean using a microphone.

There is another thread on Fark today about waning credence given to science. My opinion about reporting like this is that it can confuse or mislead readers into thinking that things like this have been settled and figured out. When some other opinion comes along, the average person becomes even more confused, and maybe resentful that they believed one team or another.

There WILL be a day, probably soon, when people will be angry that an earthquake was not predicted by experts. In fact.... it has already happened. A decade ago, a group of Italian scientists were convicted of manslaughter for NOT PREDICTING an earthquake that killed people. And that happened because people had become convinced that scientists "should have known" that an earthquake was about to occur.

"We" know very little about earthquakes, and "we" should not pretend like we do, lest we be blamed for negligence when they do occur for reasons we do not understand.

OK. Just saying that this article is fun reading. Great that people are working on this. I am skeptical. Scientific knowledge about earthquakes is somewhere between truth and Godzilla, and getting closer to truth everyday. So yay.
 
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