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Earthquakes create seismic waves capable of flattening entire cities, making early detection and prediction essential. Scientists have understood for years how earthquakes in oceanic mountain ranges at the edge of tectonic plates were tidal-related. But until now, no one could understand why there was an increase in tremors during low tides.
Professor Christopher Scholz, a seismologist at Columbia University, said, "Everyone was perplexed because, according to conventional theory, these earthquakes should occur at high tide."
But the team at the Lamont-Doherty Earth Observatory has discovered the mechanism of this apparent paradox and it is the magma below the oceanic ridges that is responsible for it.
Professor Scholz, who co-directed the study, said: "It is the magma chamber that breathes, grows and contracts under the effect of the tides, which moves the flaws.
The correlation between low tide and low tide is surprising because of the way ocean faults move.
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The fault is described as an inclined plane that separates two blocks of land.
During movement, the upper block slides downward from the lower block.
Scientists predicted that at high tide, when there would be more water over the fault, the upper block would be lowered and cause earthquakes.
But instead, the rift slips at low tide, as forces rise, "which is the opposite of what you expect," Scholz said.
The team studied the axial volcano along the Juan de Fuca Ridge in the Pacific Ocean.
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As the volcano erupts regularly about every ten years, scientists have formed dense networks of ocean floor instruments to monitor it.
The data from these instruments were used to model and explore different ways that low tides could be causing tremors.
And that 's one element nobody else has ever considered responsible: the volcano' s magma chamber, a soft, pressurized pocket under the surface.
The team realized that when the tide is low, there is less water remaining above the chamber, so it gets bigger.
As he gets up, he braids the rocks around him, forcing the lower block to slide along the rift and causing earthquakes.
In addition, said Scholz, the tidal earthquakes in this region are "so sensitive that we can see details in the response that no one could see before".
When the team compared the earthquake rate to the stress on the fault, she realized that even the smallest stress could trigger an earthquake.
Tidal data was used to calibrate this effect, but trigger stress could be caused by anything, such as seismic waves from another earthquake or fracking sewage pumped into the ground.
"People in the hydrofracking industry want to know if there is safe pressure that you can pump and that you do not produce an earthquake." said Scholz.
"And the answer we find is that there is none – it can happen at any level of stress."
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