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Arthur T Knackerbracket has found the following story:

The land masses of Japan shifted from east to west to east again in the months before the strongest earthquake in the country's recorded history, a 2011 magnitude-9 earthquake that killed more than 15,500 people, new research shows.

Those movements, what researchers are calling a "wobble," may have the potential to alert seismologists to greater risk of future large subduction-zone earthquakes. These destructive events occur where one of Earth's tectonic plates slides under another one. That underthrusting jams up or binds the earth, until the jam is finally torn or broken and an earthquake results.

[...] "What happened in Japan was an enormous but very slow wobble—something never observed before," said Michael Bevis, a co-author of the paper and professor of earth sciences at The Ohio State University.

"But are all giant earthquakes preceded by wobbles of this kind? We don't know because we don't have enough data. This is one more thing to watch for when assessing seismic risk in subduction zones like those in Japan, Sumatra, the Andes and Alaska."

The wobble would have been imperceptible to people standing on the island, Bevis said, moving the equivalent of just a few millimeters per month over a period of five to seven months. But the movement was obvious in data recorded by more than 1,000 GPS stations distributed throughout Japan, in the months leading up to the March 11 Tohoku-oki earthquake.

[...] Those movements were markedly different from the steady and cyclical shifts the Earth's land masses continuously make.

Journal Reference:
Jonathan R. Bedford, Marcos Moreno, Zhiguo Deng, et al. Months-long thousand-kilometre-scale wobbling before great subduction earthquakes, Nature (DOI: 10.1038/s41586-020-2212-1)

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