ALERT: San Diego to Los Angeles Fault System Could Produce 7.3 Magnitude Earthquake

A new analysis led by the Scripps Institution of Oceanography at the University of California San Diego revealed that the fault system that runs along San Diego, Orange County and Los Angeles County could be overdue for a major earthquake with up to magnitude 7.3.

The study, published in the Journal of Geophysical Research, showed that the Newport-Inglewood and Rose Canyon faults were actually one continuous fault system that runs from San Diego Bay to Seal beach in Orange County, and reaching inland through the Los Angeles basin.

"This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast," said Valerie Sahakian, a postdoctoral fellow at US Geological Survey and lead author of the study, in a press release. "Even if you have a high 5- or low 6-magnitude earthquake, it can still have a major impact on those regions which are some of the most densely populated in California."

For the study, the researchers analyzed data from previous seismic surveys, in addition to the high-resolution bathymetric data they have gathered between 2006 and 2009 and data from seismic surveys conducted aboard research vessels in 2013.

By mapping out the fault system, the researchers were able to identify four segments separated by the so-called stepovers, or the point where the fault is horizontally offset. Generally, stepovers wider than three kilometers are capable of inhibiting rupture along the entire fault by containing them into the segments and creating smaller earthquakes in the process.

However, the researchers found that the stepover Newport-Inglewood/Rose Canyon (NIRC) fault are just about two kilometers wide or less. Due to this, the researchers noted that a rupture of all the offshore segments is still possible. If such rapture occurred, the researchers warned that it could create magnitude 7.3 earthquakes. If the southern onshore segment of the fault system ruptured at the same time, it could trigger a magnitude 7.4 earthquake.

In 1993, the same fault system hosted a 6.4-magnitude earthquake in Long Beach, California, killing a total of 115 people.