Southern California is capable of a magnitude 7.3 earthquake, a new analysis of the region's coast fault systems revealed.
Newport-Inglewood And Rose Canyon Faults
Scientists previously believed that the Newport-Inglewood and Rose Canyon faults were separate but the new study, which was published in the Journal of Geophysical Research on March 7, revealed that the two systems are actually connected.
For the study, U.S. Geological Survey postdoctoral fellow Valerie Sahakian, and colleagues used sonar imaging to map the fault lines of the system that run from Los Angeles to San Diego. The researchers also conducted an analysis of the system's stopovers, the gaps where the faults are horizontally offset.
The findings revealed that none of the four gaps of the fault system are big enough to ensure that a future tremor will remain localized.
Earthquakes Over The Past Thousands Of Years
The fault system hosted a 6.4-magnitude earthquake near Long Beach, California in 1933. This tremor killed 115 people. Scientists also found evidence suggesting earlier earthquakes with undetermined size on onshore parts of the fault.
The northern end of the fault system had three to five ruptures over the last 11,000 years while the southern end appears to have had a tremor that occurred about 400 years ago and another one that happened 5,000 years before that.
Potentials For Powerful Earthquakes
The analysis revealed that eruption of the offshore segment of the system can produce an estimated 7.3-magnitude earthquake. If the southern onshore segment also ruptures, an estimated magnitude 7.4 earthquake may occur. The researchers found that the maximum potential for a rupture of the entire fault can produce between magnitude 6.7 and magnitude 7.3 to 7.4 earthquakes.
Looming Threat
The findings raise concerns since a powerful earthquake can have a major impact on the affected regions, which include the most densely populated parts of California. A high 5- or low 6-magnitude earthquake is already considered a threat.
Experts have earlier warned of the threats posed by the Rose Canyon fault, which could prove more damaging than the San Andreas fault. The Rose Canyon fault runs along a very populated area, which also makes it difficult to study. The location of the fault means there would be potentially fatal and costly damages when a rupture occurs.
"That is our number one threat," Ron Lane, head of emergency services for San Diego County, said in the wake of Japan's earthquake-powered tsunami in 2011. "The San Andreas for the most part - even the 7.8 magnitude prediction - does very little damage. ... It's not the big one. For us, the big one is at Rose Canyon."
Further Studies Needed To Evaluate Risks Posed By The Quake System
Scientists said that more work is needed to explore the risk that the quake system could pose to coastal cities such as Los Angeles and Tijuana.
"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 researchers concluded.
