Don't expect any cracks in walls or windows at the Cathedral of Our Lady of the Angels if The Big One (major earthquake) hits the greater Los Angeles area.

The cathedral was designed to withstand the damaging effects of earthquakes measuring up to magnitude 8.3 along the San Andreas Fault, according to Nabih Youssef, the structural engineer who designed and installed the building's base isolation system.

On Jan. 15, two days before the tenth anniversary of the devastating Northridge quake, Youssef gave a press conference down at the "plane of isolation" below the cathedral. In that one-and-a-half acre, five-foot-tall space between concrete-covered earth and the cathedral's structural slab, 149 rubber bearings and 47 "sliders" isolate the structure from ground movement resulting from an earthquake.

Located in the mechanical room underneath the cathedral, the base isolators support the 200,000-ton building, the heaviest structure that Youssef has ever designed for base isolators. Each isolator, measuring three feet in diameter and 18 inches in height, can carry a load of 500 tons.

The cathedral "floats" on the steel and vulcanized rubber isolators. They allow the building to oscillate gently above the shaking earth and have been designed to withstand horizontal earth movement as well as vertical jolts. Twenty-four groups of 16-set "loose-gap bolts" are in place to handle vertical movement.

The passive response system is designed to work immediately during a tremor. Besides the base isolators cushioning the cathedral, a five- to six-foot-wide underground air gap moat surrounding the building provides room for horizontal movement. In addition, a flexible joint piping system safeguards the plumbing.

The base isolator technology was created over 100 years ago in London to decrease vibrations to buildings located over railroad tunnels, said Youssef. The cathedral's base isolators should protect it from incurring damage during a magnitude 7.1 earthquake on the downtown Elysian Park Thrust Fault structure or a magnitude 8.3 quake on the Mohave segment of the Transcontinental San Andreas Fault located approximately 30 miles away.

Last month's earthquake centered in San Luis Opisbo County was a "test run" of sorts for the cathedral's base isolator system. While buildings in downtown Los Angeles shook, the only effect noticed by people inside the cathedral was a gentle swaying of the chandeliers, reported Franciscan Brother Hilarion O'Connor, director of operations for the cathedral.