Los Angeles ? It is the California earthquake hardly anyone has heard of – strong enough to rip 225 miles of the San Andreas Fault and make rivers run backward, but leaving nothing like the cultural scar inflicted by the San Francisco Quake of 1906.

Today marks the 150th anniversary of the magnitude-7.9 Fort Tejon quake, which was blamed for just two deaths in what was then sparsely populated California.

No museum exhibits or musical tributes will mark the 1857 event, sometimes referred to as the forgotten quake. There will be no public gatherings or bells tolling to mark the moment the ground split open, as there were for the 1906 centennial of the San Francisco quake, a catastrophe that left 3,000 people dead.

“It’ll never have the same hold on the public’s imagination as the 1906 earthquake,” said Sean Malis, an interpreter at Fort Tejon State Historic Park, a 70-mile drive high into mountains north of Los Angeles. “It’ll continue to be a footnote in history.”

Still, scientists do not want to pass up the opportunity to warn the public about the threat the fault poses and how to prepare for it. They say a repeat of Fort Tejon in the now-populous Inland Empire region east of Los Angeles – one of the fastest-growing areas in Southern California – could kill thousands of people and cause tens of billions of dollars in damage.

To drive home the point, the U.S. Geological Survey and other groups today are kicking off a yearlong campaign to warn people to prepare for the Big One. The education campaign will culminate in 2008 with what officials say will be the biggest earthquake disaster drill in U.S. history.

This aerial photo provided by the U.S. Geological Survey shows a southeast view along the surface trace of the San Andreas fault in Southern California. The Fort Tejon earthquake in 1857 caused a horizontal shift of about 30 feet near this stretch of the fault.

“We’re not trying to scare people,” said Tom Jordan, who heads the Southern California Earthquake Center. “We want to make sure that people are constantly reminded about the possibility of a much larger earthquake.”

California is prone to earthquakes because it straddles two massive plates that make up Earth’s crust. Quakes occur when the plates grind past one another along the 800-mile-long San Andreas and its offshoot faults.

While scientists cannot predict when the next quake will strike on the San Andreas, they say the southern segment that runs from the city of San Bernardino, 60 miles east of Los Angeles, to near the Mexican border is the most likely to break, since it has been building up stress for the longest time. It has not popped in three centuries.

According to some estimates, there is a 30 percent to 70 percent chance a magnitude 7.5 to 7.8 quake would rupture the southern San Andreas within the next 30 years.

“It’s really dangerous,” said seismologist Lucy Jones of the U.S. Geological Survey. “It could be any day.”

The Fort Tejon quake hit Jan. 9, 1857, breaking a 225-mile middle portion of the San Andreas from Parkfield, northwest of Los Angeles, to San Bernardino.

The ground shifted up to 30 feet in places. Rivers were reported to have run backward or been thrown out of their banks. The Army’s lonely Fort Tejon was hit hard – two buildings were left uninhabitable, and three others were badly damaged.

One woman was killed when an adobe house collapsed on her. The death toll has historically also included a man who died of a heart attack in a Los Angeles plaza.