Analysis of the fault system suggests a rupture on land could produce magnitude 7.3 earthquakes, while an combination offshore-onshore fault slip could yield magnitude 7.4 earthquakes.
His research looks at using natural disaster seismology, specifically in using quake seismic waves to study the subsurface and better understand plate tectonics. The small size of the three stepovers that link four main parts of the Newport-Inglewood and Rose Canyon fault system make them unlikely to be able to stop an quake spreading throughout the whole system. It was accepted for publication in the American Geophysical Union's Journal of Geophysical Research. "Even if you have a high 5 or low 6 magnitude quake, it can still have a major impact on those regions, which are some of the most densely populated in California".
The study looked at data from previous and new seismic surveys that included sonar studies of the offshore fault.
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.
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. The U.S. Geological Survey quake forecast maps show the risk of human-activity-induced earthquakes in Oklahoma is now as high as natural occurring earthquakes in California. Unlike other sections of the southern San Andreas, this region - about a 100-mile section of the fault - had not been studied in detail before, and scientists did not know what earthquakes occurred there before the 19th century.
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The land on either side of the fault has been pushing against the other at a rate of more than 1 inch a year since 1857, the researchers said, accumulating energy that will be suddenly released in a major quake, when the land along the fault would move by many feet. The last major temblor occurred 160 years ago, a catastrophic geological event that ruptured an astonishing 185 miles of the San Andreas fault.
The last time a major rupture of the fault took place was in Long Beach in 1933, where 115 people died in the resulting magnitude-6.4 quake.
Federal, state and military officials have been working together to draft plans to be followed when the "Big One" happens. Most scientists believe that stepovers at least 3 km wide are likely to prevent through-going ruptures.
The coast of Southern California and Tijuana, Mexico are highly vulnerable to the fault, the report indicated.