Scientists Predict Major County Earthquake : Geology: A Caltech geophysicist says the area is the second most dangerous in Southern California.

Two Ventura County mountain ranges are moving closer together each year at the geological version of dangerously high speed, creating pressure that scientists said Thursday will eventually result in a major earthquake.

The Topatopa Mountains above Santa Paula and Fillmore are pushing south and the Oak Ridge range south of those cities is moving north, with the Santa Clara River Valley caught in the middle, according to new satellite technology reported this week at the annual meeting of the American Geophysical Union in San Francisco.

The movement of about half an inch to an inch a year--considered rapid in geological time--makes a 6- or 7-magnitude earthquake along the Oak Ridge or San Cayetano faults highly probable, scientists said.

The likelihood of a major earthquake makes the Ventura County area among the most earthquake-prone regions in the world, said Andrea Donnellan, a Caltech geophysicist who presented her findings.

“There is no way around it; it’s a high hazard area,” Donnellan said. “It’s the second most hazardous area in Southern California next to the San Andreas Fault.”

Past studies of the Ventura County area by geologist Robert S. Yeats of Oregon State University have shown that a major earthquake relieves pressure created by the mountains’ movement every few hundred years. But the last major event in the area was probably in 1812, he said.

“We cannot predict when an earthquake will occur, but we can say that there will be a big one and that the county should be taking whatever time there is to prepare,” said Yeats, a former Ojai city councilman who has helped develop many of the fault maps for Ventura County.

Donnellan said scientists plan to set up more measuring stations near Santa Paula, Fillmore and Ventura and close to the Oak Ridge and San Cayetano faults. The additional stations would ensure more accurate measurements, she said.

Earlier this week, scientists at the San Francisco meeting reported that the same satellite technology had uncovered evidence of a fault 20 to 50 miles off Southern California that runs parallel to the coastline from Santa Barbara to La Jolla. The fault is still unconfirmed but presents one explanation for the kind of land movement scientists have observed, Yeats said.

Yeats said the new satellite information showing much greater movement in Ventura County than anywhere else in coastal California is a strong argument for more federal government attention to the area.

The U.S. Geological Survey has studied the earthquake hazards in the Los Angeles area because of the millions of people who could be harmed by a major event there, he said. But Ventura County, with 668,000 people, has been all but ignored.

“Ventura County needs to yell a little bit louder,” he said. Yeats has asked the USGS to formally evaluate his work and publish a statement about the risk from earthquakes in the county.

“The general feeling in Ventura County is that earthquakes happen in San Francisco and Los Angeles, and aren’t we lucky that we live here and don’t have to worry,” Yeats said. “What I’ve been saying and what the new technology is telling us is that is foolish.”

Yeats said the main danger from an earthquake in the area would be from unreinforced brick buildings in some downtown areas.

City ordinances should require that buildings be upgraded to meet seismic safety standards, he said. In Ventura and Santa Paula, which have a large number of older buildings, such ordinances have been rejected.

In Santa Paula, where 120 brick buildings house many downtown shops, the City Council rejected a proposed ordinance seven years ago, said Steven Stuart, city building and safety director.

“The building owners were very concerned, and the city had no mechanism to help finance the improvements,” Stuart said. Since then, the city has passed an ordinance asking owners to upgrade their buildings voluntarily. He said he hopes that the city will be able to form a redevelopment agency to help fund such improvements.

In Ventura, 145 unreinforced masonry buildings are subject to shaking and crumbling in a severe earthquake, said Robert Purdoehl, superintendent of building and safety. Ventura also rejected an upgrade ordinance two years ago and is now awaiting a study to outline the economic and environmental effects of requiring seismic upgrades, he said.

To receive information from the global positioning satellite, scientists set up 16 stations in and around Ventura County to provide information on how much the ground is moving.