The earthquake fault cuts through the heart of Ventura's quaint downtown, past the ornate hilltop City Hall and historic Spanish-era mission before heading into the Pacific Ocean.. For decades, some seismic experts believed the Ventura fault posed only a moderate threat and was incapable of producing a major temblor. But research in recent years shows that the fault is extremely dangerous, capable of producing an earthquake as large as magnitude 8 as well as severe tsunamis that until now experts didn't believe were possible from a Southern California quake. Such a big earthquake on the fault estimated to occur every...