Eos, Transactions American Geophysical Union

The Southern California “bulge”


  • Anonymous


The huge land uplift, or ‘bulge,’ astride a section of California's San Andreas fault—one of the most puzzling of geologic phenomena in recent years—continues to deflate or subside, according to a report from the U.S. Geological Survey.

The shrinkage in elevation of the bulge, however, has been accompanied by other changes—an increase of horizontal ‘strain’ and an increase in the emission of radon (a rare inert gas) in some wells in the region. These latest changes, revealed only recently by intensive monitoring, have only deepened the puzzle for scientists who are trying to determine the significance of the bulge as a possible precursor to a large earthquake.