Tremors that start deep underground are caused by water being controlled by the sun and moon, a new study by UC Berkeley seismologists has found.
According to ScienceDaily, the study could pave the way for better understanding of earthquakes.
The seismologists studied part of California's 800-mile San Andreas Fault, which has been responsible for some of the largest U.S. earthquakes. They found that underground fluids copy the movement of the tides causing tremors well below the level where earthquakes occur.
They believe the tremors might be making it easier for the rock to slip, weakening the fault and paving the way for earthquakes to take place.
"It is certainly in the realm of reasonable conjecture that tremors are stressing the fault zone above it," seismologist Robert Nadeau of the Berkeley Seismological Laboratory said.
"The deep San Andreas Fault is moving faster when tremors are more active, presumably stressing the seismogenic zone, loading the fault a little bit faster. And that may have a relationship to stimulating earthquake activity."
Nadeau said more research is needed to establish the relationship between the underground tremors and earthquakes.
"There is still a lot to learn about tremor and earthquakes in fault zones," Nadeau said.
"The fact that we find tremors adjacent to a locked fault ... makes you think there are some more important relationships going on here, and we need to study it more."