London: Scientists have discovered that
even faint gravitational tug of the sun and moon can set off
tremors deep underground, confirming the thousands of years
old belief of astrologers.
The American researchers, who studied the San Andreas
Fault - the infamous crack in the ground which triggered the
1906 San Francisco earthquake, found the same gravitational
tugs that create tides, also trigger small tremors that
originate around 15 miles below the ground.
The report, which will come in print in journal Nature,
said, although the pull of planetary objects is too weak to
set off a full blown quake but the findings suggest that they
could set in motion a chain of events, leading to devastation
on the surface, the Daily Mail said.
Dr Roland Burgmann, a professor of earth and planetary
science at University of California, Berkeley, said: "Tremors
seem to be extremely sensitive to minute stress changes".
"Seismic waves from the other side of the planet
triggered tremors off the coast of Washington state after the
Sumatra earthquake last year, while the Denali earthquake in
2002 triggered tremors on a number of faults in California,"
"Now we also see that tides - the daily lunar and solar
tides - very strongly modulate tremors".
American earthquake experts compared records of 2,000
small tremors in the Parkfield region 170 miles north west of
Los Angeles with the movement of the sun and moon over eight