Offshore Fault System Could Produce 7.3 natural disaster

Study Southern California Fault Systems Could Produce Magnitude 7.3 Earthquakes

Offshore Fault System Could Produce 7.3 natural disaster

A fault system that runs from San Diego to Los Angeles is capable of producing up to magnitude 7.3 earthquakes if the offshore segments rupture and a 7.4 if the southern onshore segment also ruptures, according to an analysis led by Scripps Institution of Oceanography at the University of California San Diego.

By looking through data from previous and new seismic surveys, including bathymetric data gathered offshore, the researchers estimated that the fault could cause up to a magnitude-7.3 quake if the offshore segments rupture and a magnitude-7.4 quake if that rift extends onshore. 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.

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 natural disaster, when the land along the fault would move by many feet, The Times reported.

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

"That's pretty big", Sahakian said, of the potential quake that could be generated by the new Newport/Rose fault.

Up until now the Salton trough fault (STF) managed to remain hidden, despite how well-surveyed and seismically active the state of California is, because it is underwater.

In the event of the theoretical 7.4 quake, both the the Newport-Inglewood and Rose Canyon faults would have to rupture.

This report includes material from the Associated Press.

There has been a long drought of major earthquakes on the southern San Andreas fault, which has slowly been accumulating strain as the Pacific plate grinds northward against the North American plate.

Scientists uncovered a newly identified fault line that could unleash a magnitude-7.4 quake in the region, which other researchers say is already long overdue for a whopper of a temblor along the infamous San Andreas fault.

USGS geologist Kate Scharer led a team that investigated the timing of sand, mud and gravel deposits that were episodically ripped apart by earthquakes along the San Andreas Fault over the last 1,200 years. The theoretical "Cholame" epicenter of the 1857 natural disaster is marked with the large red dot.

'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'.

Southern California Edison funded the research at the direction of the California Energy Commission and the California Public Utilities Commission.

These contingency plans reflect deep anxiety about the potential gravity of the looming disaster: upward of 14,000 people dead in the worst-case scenarios, 30,000 injured, thousands left homeless and the region's economy setback for years, if not decades. The smaller the stepover, the more likely that a rupture of one fault will be able to jump to the next. "The San Andreas for the most part - even the 7.8 magnitude prediction - does very little damage".

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