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Author Topic: Earthquakes and climate change  (Read 33370 times)

vox_mundi

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Re: Earthquakes and climate change
« Reply #100 on: June 07, 2019, 06:28:11 PM »
Solved: How Tides Can Trigger Earthquakes
https://phys.org/news/2019-06-tides-trigger-earthquakes.html

Years ago, scientists realized that earthquakes along mid-ocean ridges—those underwater mountain ranges at the edges of the tectonic plates—are linked with the tides. But nobody could figure out why there's an uptick in tremors during low tides.

"Everyone was sort of stumped, because according to conventional theory, those earthquakes should occur at high tides,"
explained Christopher Scholz, a seismologist at Columbia University's Lamont-Doherty Earth Observatory.

In a study published today in Nature Communications, he and his colleagues have uncovered the mechanism for this seeming paradox, and it comes down to the magma below the mid-ocean ridges.

... In the end, it came down to a component that no one else had considered before: the volcano's magma chamber, a soft, pressurized pocket below the surface. The team realized that when the tide is low, there is less water sitting on top of the chamber, so it expands. As it puffs up, it strains the rocks around it, forcing the lower block to slide up the fault, and causing earthquakes in the process.

Furthermore, said Scholz, the tidal earthquakes in this region are "so sensitive that we can see details in the response that nobody could ever see before." When the team charted the earthquake rate versus the stress on the fault, they realized that even the tiniest stress could trigger an earthquake. The tidal data helped to calibrate this effect, but the triggering stress could be caused by anything—such as the seismic waves from another earthquake, or fracking wastewater pumped into the ground.

Quote
... "People in the hydrofracking business want to know, is there some safe pressure you can pump and make sure you don't produce any earthquakes?" ... "And the answer that we find is that there isn't any—it can happen at any level of stress."

Open Access: Christopher H. Scholz, et.al., The mechanism of tidal triggering of earthquakes at mid-ocean ridges, Nature Communications 10, Article number: 2526 (2019)
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late