Huge quakes may rock San Francisco: Study

Washington, May 20: A big quake or a cluster of large earthquakes may shake up the

bay region of

in the coming decades, an alarming study indicated.

Seismic activity in the San Francisco bay region of California appears to follow a cyclical pattern, the scientists, who studied historical earthquake records from 1776 to 2012, noted.

The researchers also studied palaeoseismic data, which come from radiocarbon dating and evidence of movement in the layers of rock at fault sites, dating back to 1600.

Tremors in the region follow a cyclical pattern, pointing to a cluster of earthquakes between 1690 and 1776 followed by a period of low seismicity that persisted until the big quake in 1906, the findings showed.

"The idea is that stress builds up, is released and builds up again," says David Schwartz, a geologist with the US Geological Survey in California, was quoted as saying.

When the 1906 earthquake occurred, stress was released and the frequency of quakes in the region dropped dramatically, leaving the region relatively unscathed for more than a century, he added.

"we have accumulated enough stress in the Bay Area's crust that we should start to see the occurrence of more larger earthquakes, and that could be at any time," Schwartz warned.

The findings appeared in the journal Bulletin of the Seismological Society of America.

IANS