Long Beach, Calif. — Southern California’s section of the San Andreas Fault is primed for a major earthquake a leading scientist said Wednesday at the National Earthquake Conference in Long Beach.

The San Andreas Fault is one of California’s most dangerous, and the state’s longest fault. The last big quake to strike the southern San Andreas was in 1857, when a magnitude 7.9 quake struck from Monterey County to the San Gabriel Mountains near Los Angeles.

It has been quiet since then — too quiet, said Thomas Jordan, director of the Southern California Earthquake Center.

“The springs on the San Andreas system have been wound very, very tight. And the southern San Andreas fault, in particular, looks like it’s locked, loaded and ready to go,” Jordan said in the keynote talk.

Other sections of the San Andreas Fault also are overdue for a big quake. Farther southeast of the Cajon Pass, such as in San Bernardino County, the fault has not moved substantially since an earthquake in 1812, and still farther southeast, it has been relatively quiet since about 1680 to 1690.

Scientists have observed that based on how far the Pacific plate has moved northwest of the North American plate, quakes should be relieving about 16 feet of accumulated plate movement every 100 years. Yet the San Andreas has not relieved that stress in more than a century.