Two fault zones that were thought to be separate actually make up one continuous fault system running through San Diego, Orange and Los Angeles counties, according to new research.



If all the offshore and onshore segments of the so-called Newport-Inglewood/Rose Canyon fault system were to rupture at once, a magnitude 7.4 earthquake could seize the region.

“The size of an earthquake is directly related to the length of the fault that’s rupturing — the longer the fault, the larger the earthquake,” said Valerie Sahakian, a researcher at the United States Geological Survey, who led the study as a postdoctoral researcher at the Scripps Institution of Oceanography.

While previous research had suggested that breaks in the Newport-Inglewood and Rose Canyon faults were as wide as three miles, Dr. Sahakian’s team found that these gaps were no more than 1.25 miles wide.