Research Highlight: Fault System off Southern California Could Produce Magnitude 7.3 Quake

Posted March 09, 2017

Prior to this study, the Newport-Inglewood and Rose Canyon faults were believed to be separate systems.

The frightening revelation comes from a new study led by Scripps Institution of Oceanography, which found that the Newport-Inglewood and Rose Canyon faults are connected. These segments are separated by what geologists term as stepovers, which are where a fault is horizontally offset. With this information, they defined the fault dimensions and magnitude with more precision than other studies before.

The U.S. Geological Survey has released a new study that says we could be overdue for a major quake from the San Andreas Fault along the Grapevine - in the Tejon Pass near Frazier Mountain in northeastern Kern County - that would shake the Los Angeles basin for several minutes.

The findings raise concerns since a powerful quake can have a major impact on the affected regions, which include the most densely populated parts of California.

Sahakian and her team used two earthquake-strength estimation methods and found that an quake would be estimated between a magnitude 6.7 and 7.4.

The re-identified fault, which includes the Newport-Inglewood and Rose Canyon lines, runs between Los Angeles and San Diego could set off a 7.4 magnitude quake, according to a report issued Tuesday in the Journal of Geophysical Research by scientists from UC San Diego and Scripps Institution of Oceanography.

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The study was led by Valerie Sahakian, who earned her doctorate at Scripps before moving to the U.S. Geological Survey as a postdoctoral fellow.

When conducting research, the team processed seismic surveys from the past and added in high-resolution bathymetric data, gathered offshore by Scripps researchers between 2006 and 2009, in addition to seismic surveys conducted aboard former Scripps research vessels.

Researchers analysed the latest data from the state's complex system of active geological faults, as well as new methods for translating these data into natural disaster likelihoods.

This Temblor figure shows the Southern California coastline both with and without faults. We're talking about a really big natural disaster along the southern end of the San Andreas Fault that measures magnitude 7.5 or greater. The 1933 Long Beach quake at the fault was magnitude 6.4, killing 115 people. Researchers found that there have been between three and five earthquakes along the northern part of the fault line in the last 11,000 years.

'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'.