Many foot tsunami could hit california

A new study calls attention to the tsunami hazard posed by a little-understood jumble of seafloor faults off the coast of Southern California — just in time to ride the wave of hype generated by the big-budget disaster movie "San Andreas.

The study's lead author, geologist Mark Legg, says a real-life offshore earthquake and tsunami wouldn't exactly follow Hollywood's script for a washout of Los Angeles or San Diego. Nevertheless, he says the hazard deserves more attention than it's received.

"That has not been looked at carefully when it comes to the potential for large earthquakes and tsunamis from offshore faults," Legg, who runs a Southern California consulting firm called Legg Geophysical, told NBC News.

Other earthquake experts insist the hazard has been looked at, but they acknowledge that the offshore faults are worthy of further study. "It's a complicated picture, and this is an important piece of it," said Lucy Jones, science adviser for risk reduction in the U.S. Geological Survey's Natural Hazards Mission Area.

Legg's latest research paper, accepted for publication in the Journal of Geophysical Research: Earth Surface, looks at a mostly underwater seismic region known as the California Continental Borderland. He said surveys of the region show a "complicated logjam" of faults caused by the smash-up of the Pacific tectonic plate and the North American plate.

The research draws upon mapping data from a depth survey in 2010 that covered more than 2,800 miles (4,500 kilometers) of fault lines on the ocean floor, plus data from earlier surveys. Legg and his colleagues focused on two fault zones in the Borderland — the Santa Cruz-Catalina Ridge Fault and the Ferrelo Fault.

Based on their measurements, the researchers determined that the seafloor crust in those areas was subject to horizontal strike-slip forces as well as vertical compression. Computer models showed that the offshore faults were capable of generating magnitude-8 earthquakes.

Legg said earlier underwater surveys found evidence of vertical movement along faults in the Borderland, amounting to as much as 10 feet (3 meters) — the kind of movement that can generate tsunami waves. "There's a smoking gun," Legg said.