Prior to this study, the Newport-Inglewood and Rose Canyon faults were believed to be separate systems.
The newly identified fault line is capable of a powerful quake that would impact 20 million residents of Los Angeles and San Diego, according to a study published Tuesday.
The Newport-Inglewood/Rose Canyon fault zone exhibits a mainly continuous fault trace over four distinct segments. With this information, they defined the fault dimensions and magnitude with more precision than other studies before.
According to the 53 pages study, researchers used two methods to reach these conclusions about the possibility of a big natural disaster in California.
San Diego - A recent study of the Institution of Oceanography at the University of California San Diego (UCSD) shows that there is a significant fault between San Diego and Los Angeles that could be the cause of a magnitude 7.4 natural disaster in California. Since the stepovers are only 1.24 miles wide at most, the team concluded that the points are not wide enough to inhibit a rupture of the entire offshore segments.
Lead author of the study Valerie Sahakian, who studied at Scripps and is now at the U.S. Geological Survey, said in a statement: "This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast".
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While the likelihood of a full rupture sits at 30-40%, lead author Valerie Sahakian, who is now a postdoctoral fellow at the USGS in Menlo Park, says that a smaller natural disaster in the magnitude 5 or 6 range could still have a significant impact on the region.
The researchers used data from previous seismic surveys, along with high-resolution bathymetric offshore data from Scripps research between 2006 and 2009, and seismic surveys conducted aboard former Scripps research vessels New Horizon and Melville in 2013. Southern California Edison funded the research at the direction of the California Energy Commission and the California Public Utilities Commission.
And, evidence of earlier quakes of an unknown size reveal the onshore portions have experienced between three and five ruptures in the last 11,000 years.
The last major natural disaster on the Newport-Inglewood/Rose Canyon fault was the 1933 magnitude 6.4 quake in Long Beach, which killed 115 people and spurred changes in, among other things, school construction. As a result, an natural disaster triggered at the fault could reach up to magnitude 7.4.
The southern end also shows evidence of an event roughly 400 years ago, though there is little significant activity in the 5,000 years leading up to it. It concluded that further study was needed to better understand the hazard potential in the area.