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.

[Steve Van Doorn]

said, "I imagine it’s a matter of the planet’s rotation distributing mass equally, to the extent possible."
nice way to put it. What do you think will happen when the sun and the earth magnetic poles shift?

[Harmless Teddy Bear]

Golly-zilla?

Or Cthulhu?

[gundog]

Mass hysteria. Just the planet and the sun doing what they do. People will do what people do, too, and it won’t be pretty.

[SunkenCiv]

Thanks BenLurkin.

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While there have been hints of lower mantle quakes before, researchers have struggled to pinpoint them within this layer of the Earth.

[Steve Van Doorn]

Hysteria maybe.
Heinrich event ... won’t be pretty.

[Berosus]

Did this earthquake generate a tsunami?

[gleeaikin]

When did Japan’s great tsunami and earthquake occur. Fukushima?

[DannyTN]

4/11/2011. So 10.5 years ago.

[gleeaikin]

After what happened in Japan 10.5 years ago, I guess they were paying even more focused attention 6 years ago.

[DannyTN]

I bet they were!