43% Chance Seen of Quake Damaging L.A. in 30 Years

SAN FRANCISCO —  A UCLA earthquake expert said Wednesday there is a 43% chance of an earthquake strong enough to do at least some damage in Los Angeles in the next 30 years.

David D. Jackson said San Bernardino has a 63% chance of such a quake, which he said would be marked by shaking equal to at least 20% of the force of gravity--the equivalent of at least a magnitude 5.5 quake, according to seismologists with the U.S. Geological Survey.

If such a quake occurs in the heart of Los Angeles, buildings would sustain damage but it probably would not be major, according to the agency.

Officials noted that in the last 30 years, the Los Angeles area has sustained three local quakes stronger than that--the magnitude 6.4 Sylmar-San Fernando in 1971, the 5.9 Whittier Narrows in 1987 and the 5.8 Sierra Madre in 1991. So, they said, the panel’s new probability is hardly a shocking warning.

Jackson heads the working group of a scientific panel charged with assessing quake probabilities for Southern California.

Last month, directors of the panel of 40 scientists said they were divided on the overall probabilities in the next 30 years of a major quake, magnitude 7 or bigger, somewhere in Southern California. They said they would delay any official announcement of their conclusions until at least next March.

Jackson said that depending on which computer model it is using, the panel now believes that the probability in that time period may range anywhere from 55% to 85% of a major quake occurring on one of the many faults that crisscross Southern California.

He added that the panel believes the chance of a big quake happening on the southern San Andreas fault is 50% during that period. This is a little less than the 60% chance an earlier scientific panel estimated on the southern San Andreas within 30 years when it evaluated the situation in 1988.