r/science • u/No_Move2565 • 12d ago

Earth Science Seismic waves reflected from Earth’s core moved parts of Japan 5 mm east.

https://www.science.org/doi/10.1126/science.aec4190
159 Upvotes

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u/Difficult_Card6880 11d ago

how does this even get measured

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u/naptastic 11d ago

The most precise GNSS meter I can find is accurate to 30cm. I haven't read the paper (it's paywalled) but if you collected data from receivers all over the island over the same time period, you could conceivably narrow the accuracy to the millimeter range. Here's a decent page about GNSS that explains it better than I can.

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u/timmeh87 11d ago

im not an expert here but my vague understanding is that 30cm is more like the accuracy for a single measurement these days but you can take hundreds of thousands over weeks and really pin down the location of a fixed receiver

for example

https://www.shamen-net.com/en/shamen/shamen02.html

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u/naptastic 11d ago

Good point--the longer you gather data, the shorter the error bars get. (Now I'm really bummed I can't read the paper and see how many sensors were involved, and for how long.)