New quake study raises alarm on west coast

San Diego, Calif. — An earthquake fault running from San Diego Bay to Los Angeles is capable of producing a magnitude-7.4 earthquake that could affect some of the region's most densely populated areas, according to a study released Tuesday.

The study looked at the Newport-Inglewood and Rose Canyon systems - previously thought to be separate - and concluded they actually form a continuous fault that runs underwater from San Diego Bay to Seal Beach in Orange County and on land through the Los Angeles basin.

The fault poses a significant hazard to coastal Southern California and Tijuana, Mexico, according to the study. It could produce up to a magnitude-7.3 quake if the offshore segments rupture and a magnitude-7.4 quake if the onshore segment also ruptures, according to the study by Scripps Institution of Oceanography at the University of California San Diego.

Even a moderate quake on the fault could have a major impact on the region, according to Valerie Sahakian, the study's lead author. "This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast," Sahakian was quoted as saying in a press release from the American Geophysical Union.

The fault's most recent major rupture occurred in 1933 in Long Beach and produced a magnitude-6.4 earthquake that killed 115 people.