SoCal Fault Could Cause Stronger Shaking: New UC Riverside Study

RIVERSIDE COUNTY, CA – IMAGE: The figure shows the location of the Ventura-Pitas Point fault with respect to the cities involved. The view is of Southern California, as seen from the Pacific coast looking east. The thin white line is the coastline; the outlines of the Channel Islands can be seen off to the right (the south). The pink triangulated surface is the Ventura-Pitas Point fault. At the edge of it can be seen the stair-step cross-section, the flat part being under Santa Barbara.

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A fault line running beneath the city of Ventura and out to sea appears to have wider dimensions than originally thought and could produce major shaking in the event of an earthquake, according to a study co-authored by a UC Riverside professor.

Department of Earth Sciences Associate Professor Gareth Funning, working with a team from institutions throughout the country, performed analyses showing that the Ventura-Pitas Point fault has a shape that's likely conducive to damaging quakes.

"Our models confirm that the Ventura-Pitas Point fault is a major fault that lies flat under much of the coast between Ventura and Santa Barbara," Funning said. "This means that a potential source of large earthquakes is just a few miles beneath the ground in those cities. We would expect very strong shaking if one occurred."

Funning and his colleagues published their findings in the most recent edition of Geophysical Research Letters. The title of their thesis is "Mechanical Models Favor a Ramp Geometry for the Ventura-Pitas Point Fault, California."

The researchers used GPS and other data to map the fault's dimensions, which from the late 1980s to 2014 had been assumed to represent a planar configuration, dipping 13 miles below the surface.

A different geometry emerged from a study published three years ago, and Funning and his associates used some of that information to conclude that the fault may be closer to a staircase shape that slopes beneath Santa Barbara and Goleta, stretching through the Santa Barbara Channel, according to UCR.

The findings point to the potential of magnitude-8 quakes with intense shaking, raising the risk of greater surface damage and tsunamis, according to the researchers.

Funning was joined by Hannah Krueger and Scott Marshall of Appalachian State University, John Loveless of Smith College and Susan Owen from NASA's Jet Propulsion Laboratory in authoring the work, which will continue with simulations to more accurately gauge the potential depth and intensity of quake activity along the fault.

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--City News Service/IMAGE CREDIT: GARETH J. FUNNING AND SCOTT T. MARSHALL.