LOS ANGELES (AP) -- Scientists say they have detected a spike in underground rumblings on a section of California's San Andreas Fault that produced the 1857 magnitude-7.8 earthquake.

What these mysterious vibrations say about future earthquakes is far from certain.

Some think the deep tremors suggest underground stress may be building up faster than expected, and may indicate an increased risk of a major temblor.

So the question that has been asked for years is being asked again - is 'The Big One' coming? Scientists know a major earthquake is possible in southern California, however the bigger question is when will it happen. Some scientists believe a major earthquake could happen anytime, between the next three minutes, and the next 30 years.

The new study by scientists at the University of California, Berkeley appear in Friday's issue of the journal Science.