The Los Angeles area has enough water in reserve should an earthquake break the California Aqueduct, Metropolitan Water District officials said. Their statement followed a report from Dr. Clarence Allen of the Caltech seismology laboratory, which indicated that a major earthquake could break the aqueduct. Bob Gompers, a water district spokesman, said that Allen's report focused on a proposed expansion of the east branch of the system, which would result in the aqueduct crossing the San Andreas Fault in three places. Gompers said that geologists throughout the world have predicted that an earthquake measuring 8.5 on the Richter scale will strike Southern California in the next 25 to 50 years. Allen's study showed that the aqueduct would break in a large temblor, Gompers said. But water in various reservoirs would last about six months, more than enough time to make repairs, he said.