Analysts studied four sections of the fault that were offset (stepovers), and discovered the separations were not extensive enough to avert a split of the whole offshore segment of the fault. Finer mapping of the region showed that the faults are actually closely connected, according to a study in in the Journal of Geophysical Research.
"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, who lead the study during her doctorate at Scripps.
According to the 53 pages study, researchers used two methods to reach these conclusions about the possibility of a big natural disaster in California.
The findings raise concerns since a powerful natural disaster can have a major impact on the affected regions, which include the most densely populated parts of California.
A new study confirms what many Angelenos already know in their heart of hearts: Sooner or later, the San Andreas Fault will will wreak havoc on Los Angeles.
Stepovers wider than three kilometers (1.86 miles) are usually considered to inhibit large earthquakes, containing the ruptures to small segments instead of along entire faults.
A report from the U.S. Geological Survey has warned the risk of "the big one" hitting California has increased dramatically.
The study used data from older seismic surveys as well as high-resolution offshore bathymetric (underwater topography) data collected by Scripps researchers between 2006 and 2009.
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.
This Temblor figure shows the Southern California coastline both with and without faults.
The research found earthquakes happen there on average every 100 years, the Los Angeles Times reported.
The find means the entire system could be capable of producing more powerful earthquakes than previously expected, with up to a magnitude 7.3 if the offshore segments rupture, and 7.4 if the onshore portion breaks as well. A high 5- or low 6-magnitude quake is already considered a threat. At the southern end, there is evidence of a quake that took place roughly 400 years ago and little significant activity for 5,000 years before that.
"Further study is warranted to improve the current understanding of hazard and potential ground shaking posed to urban coastal areas from Tijuana to Los Angeles from the NIRC fault", the study concludes.