Rumbles deep underground are caused by water being controlled by the sun and moon, University of California, Berkeley, seismologists concluded in a new study that could lead to a better understanding of earthquakes.

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WALNUT CREEK, Calif. — Rumbles deep underground are caused by water being controlled by the sun and moon, University of California, Berkeley, seismologists concluded in a new study that could lead to a better understanding of earthquakes.

The study of a portion of the San Andreas fault revealed that underground fluids move like the tides, the scientists wrote in an article published Wednesday in the journal Nature.

Geologists had long wondered what caused the frequent rumbling 15 miles below the surface, said co-author Roland Burgmann, a Berkeley professor of earth and planetary science.

“People had looked for those kinds of relationships for decades,” said Burgmann, who wrote the paper with seismologist Robert Nadeau and doctoral student Amanda Thomas. “Now, with these tremors, there’s a very strong relationship.”

Highly pressurized water essentially lubricates certain faults, including the San Andreas in California, far below the portion of the fault that causes measurable earthquakes, scientists found.

The relationship between the deep tremors and earthquakes remains unclear, Nadeau said.

Though scientists noted that a major 2002 Alaska earthquake set off deep tremors on other parts of the planet, it was not previously known the sun and moon could have a similar effect, said Kenneth Creager, a professor of earth sciences at the University of Washington.

“Seeing that (underground water) is sensitive to even smaller stresses is significant,” he said.