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A 35-mile fault stretching from Santa Rosa to San Pablo Bay in Northern California's wine country appears to be under extreme pressure and could rupture with a major shake, scientists report.

U.S. Geological Survey scientist David Schwartz said he would lead a scientific team into the area within a few weeks to study the little-known Rodgers Creek Fault in Sonoma County.The warning came Friday at a Seismological Society of America meeting in Santa Cruz, near the epicenter of last October's 7.1 magnitude earthquake that killed 62 people and caused some $5 billion in damage in Northern California.

Seismologist Ivan Wong, a geological consultant reviewing quake risks to landfills in Sonoma County, said the Rodgers Creek Fault has been ominously free of tiny quakes that relieve locked-up ground pressures in active fault lines.

This lack of activity creates a "seismic gap" - or recognized point of extreme pressure buildup that could lead to a rupture - said Wong.

Scientists identified the Loma Prieta area of the Santa Cruz mountains as a seismic gap along the San Andreas Fault before the Oct. 17 quake centered in the region.

Schwartz, who previously sounded an alarm over the the Rodgers Creek Fault, said studies also indicate the fault could stretch 5 or 10 miles further north than previously believed, adding greater potential for a large quake.

Schwartz said he will lead a team to increase the number of trenches in the rolling ranchland between Sonoma and Petaluma. Similar 12-foot deep trenches dug across the fault last year, he said, showed three to four major earthquakes there in the past 1,300 years.

Records going back to 1808, however, said Schwartz, make no mention of a big quake in the area. The new trenches, he said, may yield evidence as to when the last major shake took place.

A 7.0 magnitude quake on the fault, said Schwartz, "would undoubtedly cause more damage than we saw October 17" with the nearby towns of Santa Rosa, San Rafael, Richmond, Vallejo and other north bay cities being severely shaken.

Wong said another seismic gap exists along the even bigger Mayacamas Fault that stretches northeast of Santa Rosa to Ukiah, a distance of about 50 miles.

University of Nevada, Reno, scientist Peggy Johnson said another dangerous area because of lack of activity is on the California-Nevada border in the White Mountains east of Mono Lake.