LOS ANGELES - A major earthquake along the San Andreas fault could bring Hurricane Katrina-scale devastation and disruption to Southern California, earthquake scientists and government officials warned Tuesday as they kicked off a yearlong campaign to ratchet up emergency planning and encourage residents to prepare for the inevitability of a powerful quake.

Speaking on the 150th anniversary of the largest earthquake in California's recorded history - a magnitude 7.9 temblor on a section of the San Andreas fault near San Bernardino - the scientists said new computer simulations show that a quake of similar magnitude along the fault today would cause shaking stronger and longer than previously predicted.

Such a quake - lasting up to four minutes - would cause an estimated 150 deaths, 5,000 injuries and $150 billion in economic damage, primarily to homes around the region, said Patricia Grossi, an earthquake risk specialist with RMS, a risk management firm.

Thomas Jordan, director of the Southern California Earthquake Center at the University of Southern California, said there is a 30 percent to 70 percent chance of a 7.9-magnitude quake on the southern part of the San Andreas fault over the next 30 years.

"To seismologists like me, (this section of the fault) could be said to be nine months pregnant," he noted.

The southern section of the San Andreas fault begins in Parkfield, in central California, and runs hundreds of miles south, past the Riverside-San Bernardino area, Palm Springs and the Salton Sea to the Mexican border and beyond.

Jordan said that because of Southern California's geology, Los Angeles would take the brunt of a major earthquake centered in Palm Springs, where many scientists believe the San Andreas fault is particularly overdue for a rupture.