Deepest earthquake ever detected struck 467 miles beneath Japan

National Geographic ^ | OCTOBER 25, 2021 | MAYA WEI-HAAS

[BenLurkin]

The first jolt, which struck off the coasts of Japan’s remote Bonin Islands, was recorded at magnitude 7.9 and up to 680 kilometers (423 miles) underground, making it one of the deepest quakes of its size. Then another oddity emerged in the cascade of aftershocks that followed: a tiny temblor that, if confirmed, would be the deepest earthquake ever detected.

The ultradeep quake, described recently in the journal Geology, is estimated to have struck some 751 kilometers (467 miles) beneath the surface in the layer of our planet known as the lower mantle, where scientists have long thought earthquakes unlikely, if not impossible. While there have been hints of lower mantle quakes before, researchers have struggled to pinpoint them within this layer of the Earth.

“This is by far the best evidence for an earthquake in the lower mantle,” says Douglas Wiens, a seismologist specializing in deep quakes at Washington University in St. Louis who wasn’t part of the study team.

Some scientists caution that more research is needed to confirm the quake is real and did indeed strike in the lower mantle. While the boundary sits an average of 660 kilometers (410 miles) underground, it can vary around the globe. Under Japan, the lower mantle is believed to start about 700 kilometers (435 miles) down. The team detected several aftershocks around this depth—but one particular quake sat well beyond.

[Samurai_Jack]

drums in the deep!

[noiseman]

Here, let me save everyone else the effort: Godzilla!

[mylife]

[billorites]

We're so screwed.

[Fish Speaker]

Beat me to it ...

[xp38]

ゴジラ

[mewzilla]

Graboids!

[conservativeimage]

6 years ago...

[Dr. Sivana]

No one has blamed this on fracking in Pennsylvania yet?

[Veto!]

Worry, worry, worry.

And how long have we been “detecting” them? For a very short time in Earth’s history.

Worry, worry, worry.

[BenLurkin]

http://www.lerctr.org/~transit/healy/offsides2.wav

[Repeal The 17th]

People have a tendency to imagine the tectonic plates
as being two-dimensional, but they are obviously 3-dimensional
and the exact depth and deep boundaries and pretty much unknown.

[Vermont Lt]

Godzilla!

[Steve Van Doorn]

"(tectonic plates) are obviously 3-dimensional and the exact depth and deep boundaries and pretty much unknown"

My question is do they float on the magma? What keeps them from surging relative to the magma? Think of India and how it moved from South Africa to where it is.

[DannyTN]

Yikes.

Dutchsinse says deep earthquakes are usually followed by shower earthquakes a magnitude of order larger.

So a 7.9 deep earthquake will likely result in a shallower 8.9 nearby. If I understand his forecasting methods correctly.

I think he just went live on twitch.

[DannyTN]

shallower earthquakes, not shower earthquakes.

[DannyTN]

Oh the article is talking about something that happened 6 years ago.

[Repeal The 17th]

“...do they float on the magma...”
-
That is the way I visualize them.
But huge thick chunks, not thin slivers.

[gundog]

I imagine it’s a matter of the planet’s rotation distributing mass equally, to the extent possible.