A section of the San Andreas Fault responsible for causing a massive 7.8 earthquake in 1857 recently showed a spike in rumblings, scientists said, as they grow concerned of a major earthquake.

"The persistent changes in tremor suggest that stress is now accumulating more rapidly beneath this part of the San Andreas Fault, which ruptured in the ... magnitude 7.8 Fort Tejon earthquake in 1857," researchers said in their report.

Fort Tejon is in a region in southern California that suffers a major earthquake every 85 to 142 years, and is now 10 years overdue for a large quake.

In the town of Parkfield, located about 175 miles south of San Jose, University of California-Berkeley seismologists say tremors along the San Andreas Fault have increased 80 percent over the past four years.  UCB seismologist Robert Nadeau and graduate student Aurelie Guilhem published their findings in the latest edition of Science, although doesn't give a possible time frame when a major earthquake could strike.

"We've shown that earthquakes can stimulate tremors next to a locked (fault) zone, but we don't yet have evidence that this tells us anything about future quakes," Nadeaus said in an official statement.  "But if earthquakes trigger tremors, the pressure that stimulates tremors may also stimulate earthquakes."

Since July 2001 to February 2009, more than 2,000 tremors -- lasting from a few minutes up to around 30 minutes -- and a 6.5 and 6.0 magnitude earthquakes occurred in 2003 and 2004.  The research was partially funded by the U.S. Geological Survey and National Science Foundation, as the government wants to evaluate the likelihood of a major quake hitting California.

It's unknown what is causing the tremors, as researchers don't think they're volcanic -- it's possible underground fluid movement, or pieces of sharp rock are hitting soft rock.